National Income Determinationand Price Level:Aggregate Supply andAggregate Demand Model

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National Income Determination and Price Level:

Aggregate Supply and Aggregate Demand Model National Income Determination

and Price Level:

Aggregate Supply and

Aggregate Demand Model

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Background

This resource pack is published to support the learning and teaching of Topic G in the Economics Curriculum. It is written in accordance with the Economics Curriculum and Assessment Guide (Secondary 4-6) – Supplementary Document. During the review of New Senior Secondary Curriculum and Assessment conducted in 2013, the sub-topic of Topic G “reasons for an upward sloping short run aggregate supply curve” was fi ne-tuned. Starting from S4 in 2013/14, i.e.2016 HKDSE Examination, students are expected to grasp “imperfect adjustment of input and output prices” as the ONLY explanation required. While the examinations before 2016, the three theories namely, sticky-wage theory, sticky-price theory and misperception theory are still required and they are also included in this booklet.

This booklet does not only include the illustration and analysis of the aggregate supply and aggregate demand model, Budget 2014-15 is also incorporated for illustrating the application of the model.

This resource pack was uploaded to the website of the Education Bureau (http://www.edb.gov.hk) for teachers’ reference. If you have any comments and suggestions on this pack, please send them to:

Chief Curriculum Development Offi cer (Personal, Social and Humanities Education) Curriculum Development Institute

Education Bureau 13/F., Wu Chung House 213 Queen’s Road East Wanchai, Hong Kong Fax.: 25735299

E-mail:ccdopshe@edb.gov.hk Curriculum Development Institute Education Bureau

13/F., Wu Chung House 213 Queen’s Road East Wanchai, Hong Kong Fax.: 25735299

E-mail:ccdopshe@edb.gov.hk

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One of the most important issues of macroeconomics is the determination of output and price levels. The reasons for economists’ concern of income and price determination are obvious.

The output level of an economy closely links with the levels of employment and economic well- being of the households. The economic downturn caused by the global fi nancial crisis in 2008 best illustrates this point. From the fourth quarter of 2007 to the second quarter of 2009, the output (i.e. GDP) of the U.S. dropped by 4 percent in real term while the unemployment rate escalated from 4.4 percent in May 2007 to 10.1 percent in October 2009. The living standard of the Americans was adversely affected. The situation was not confi ned in the U.S. It took place around the world, in particular the European countries. Of equal importance in macroeconomics is the changes in price level. A rapid rise in price levels, in both factor and product markets, is another concern for households and fi rms as the former face declining purchasing power while the latter confront rising costs, such as the situation found in the U.S. in the 1970s during which price level rose 7 percent per year.

In this teaching pack, we will fi rst use an aggregate-supply-and-aggregate-demand (AS- AD) model to analyse the determination of output and price levels. We will then illustrate how changes in AD and AS affect the output and price levels. It may be more straightforward to start with the AD curve and explain to students clearly why it is downward sloping by looking into the wealth effect, interest-rate effect and exchange-rate effect. However, it is advisable that no matter what effect you discuss, start with price changes and end with output changes. Students will have a more concrete idea how price level changes affect output level. After students grasp fi rmly on the shape of the AD curve, it is important to let them realize that the AD curve represents the aggregate demand for all goods and services in the whole economy, but not a market demand curve for an individual product that they learn in microeconomics.

When you explain the vertical long run AS curve, emphasize fi rst, the production capacity

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of an economy in the long run depends on the availability of resources such as capital, labour and natural resources, and second, prices are fully adjusted in long run and so prices will have no effect on output. After that, you may move to discuss the upward-sloping short run AS curve by focusing on the absence of capacity constraints and the imperfect adjustment of input and output prices in the short run. Don’t scare the students by going into details of the three theories, namely the Sticky-Wage Theory, the Sticky-Price Theory, and the Misperception Theory, in explaining why short run AS curve is upward-sloping as the distinction among the three theories is subtle for some students. That said, some more capable students may fi nd the theories interesting, though challenging.

After examining the AD and AS curves, you can lead your students to use the curves to determine output and price levels. To enable students to learn more systematically, you may use the 4-step hints in the box on page 28. Use different real world cases and follow the steps to illustrate how AD and AS curves explain changes in output and price levels.

The AS-AD model is one of the most challenging, but useful, models for economics students. Once they acquire a solid understanding of the model, they will fi nd it very instrumental to understand a number of macroeconomic issues in subsequent topics. Hard work pays off!

Charles Kwong Jan 2014

iii

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Background ...i

Preface ...ii

Contents ...iv

Learning Outcomes ...1

1. Introduction ...2

2. Aggregate Demand ...2

2.1 What is aggregate demand ...2

2.2 What is an AD curve ...3

2.3 Why is aggregate demand curve downward sloping ...3

2.4 Determinants of aggregate demand ...8

3. Aggregate Supply ...12

3.1 What is aggregate supply ...12

3.2 What is an aggregate supply curve ...12

3.3 Why is the long run aggregate supply curve vertical ...12

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3.4 What are the factors shifting LRAS curve ...14

3.5 Why is the short run aggregate supply curve upward sloping ...16

3.5.1 Absence of capacity constraints ...17

3.5.2 Imperfect adjustment of input and output prices ...17

3.6 What are the factors shifting the short run aggregate supply curve ...21

3.7 Concluding remark ...21

4. Determinants of equilibrium levels of output and price in the AS-AD model ...22

4.1 Determinants of equilibrium output and price levels in the long run ...22

4.2 Changes in equilibrium levels of price and output ...23

5. Application of the AS-AD Model: The case of Budget 2014-15 ...29

5.1 Highlights of the Budget ...29

5.2 How does the Budget affect our macroeconomy ...30

References ...33

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After completing this topic, students should be able to

explain why the aggregate demand (AD) curve is downward sloping, identify and understand the determinants of AD,

explain why the long run aggregate supply (LRAS) curve is vertical,

explain why the short run aggregate supply (SRAS) curve is upward sloping, identify and understand factors affecting LRAS and SRAS,

Learning Outcomes

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National Income Determination and Price Level:

Aggregate Supply and Aggregate Demand Model 2

1 Introduction

Topic F tells us how to compile Gross Domestic Product (GDP) which measures the total value of production of all resident producing units of an economy in a specifi ed period (typically a year or a quarter), before deducting the consumption of fi xed capital. Empirically, for most of the countries, particularly for those advanced countries, GDP demonstrates an upward trend in the long run. However, in the short run, we observe that GDP fl uctuates around this long term trend. During economic booms, consumption increases and fi rms invest more, GDP goes up. During recessions, consumers spend less and fi rms cut its investment, GDP goes down. The ups and downs of GDP not only affect the living standards, but also employment level of an economy.

In this unit, we use an aggregate demand (AD) and aggregate supply (AS) model to analyse the determination of output and price levels. We will then illustrate how changes in AD and AS affect the output and price levels. After that, we will discuss the relationship between output and employment levels.

2 Aggregate Demand

2.1 What is aggregate demand?

GDP (Y) is made up of four components:

consumption (C), investment (I), government expenditure (G), and net exports (NX). Each of the four components is a part of aggregate demand (AD). Then we have:

Y = C + I + G + NX

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2.2 What is an AD curve?

An AD curve shows the relationship between price and the quantity of output (real GDP) demanded by the households, fi rms, the government and foreign sectors.

2.3 Why is the aggregate demand curve downward sloping?

Figure 1 shows a downward sloping AD curve which indicates that, other things remain constant, a fall in the price level raises the quantity of goods and services demanded. Conversely, a rise in the price level reduces the quantity of goods and services demanded. This means that to understand why the AD curve slopes downward, we must understand how changes in the price level affect consumption, investment, and net exports. Government expenditure is assumed to be fi xed by policy, not by price level. Thus it is not included in the analysis at this stage.

Price level

0 Output

AD

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I. The Wealth Effect: The Price Level and Consumption

A household’s wealth is the difference between the value of its assets and the value of its debts. For example, if you hold all your $10,000 assets in cash and you have no debt, your wealth is $10,000.

Suppose that the price level unexpectedly drops by 20%, the real value of your wealth will increase by 20% as your purchasing power has increased. A fall in the price level makes consumers become wealthier, which in turn encourages them to spend more. The increase in consumption spending means a larger quantity of goods and services demanded.

II. The Interest-Rate Effect: The Price Level and Investment

When the price level is lower, households needs less money to buy goods and services. They withdraw less and borrow less money from the banks. They need to sell less fi nancial assets, such as bond, in the market. All these add liquidity (i.e. funds) in the fi nancial market and interest rates will fall.

A fall in interest rates encourages borrowing by fi rms that want to invest in new plants and equipment.

Thus, a lower price level leads to a fall in the interest rate, encourages greater spending on investment goods, resulting in an increase in the quantity of goods and services demanded.

(Note: Teachers can revisit the following analysis with students after they have acquired the concepts about money market.)

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When the price level falls, the quantity of money required for a given amount of transaction would decrease. Hence the quantity of money demanded at each interest rate would decrease, the money demand curve will shift to left (MD₁ to MD₂) and the interest rate will decrease from r₁ to r₂.

Figure 2 A fall in money demand

Relationship between price level and interest rate- money market

interest rate (r)

Quantity of money MS

0 MD

₁

MD

₂

r

₂

r

1

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III. The Exchange-Rate Effect: The Price Level and Net Exports

As discussed in the previous section, a lower price level decreases interest rate. Suppose a fall in the price level in the United States lowers the U.S. interest rate. American investors will gain higher returns by investing abroad. Increasing U.S. capital outfl ow raises the supply of U.S. dollars in the foreign exchange market. U.S. dollars will then depreciate (i.e. price of U.S. dollars decreases). In terms of U.S. dollar, U.S. goods become relatively cheaper than foreign goods. Exports rise and imports fall. Net exports increase, thereby raising the quantity of goods and services demanded in the U.S.

(Note: If students fi nd diffi culty in understanding the above illustration based on the concepts of capital fl ow and exchange rate, they may use the following analysis to explain the relationship between price level and net exports.)

Net exports (NX) is equal to the value of exports (X) minus the value of imports (M). Suppose the price level of Country A decreases and becomes relatively lower than that in other countries, Country A’s exports will become less expensive and foreign imports will become relatively more expensive. Consumers in foreign countries will shift their consumption from domestic products to importing Country A’s products, and consumers in Country A will also shift from buying imported products to buying domestic products. Hence Country A’s exports will increase and its imports will decrease. Country A’s net exports will in turn increase. It means the quantity of goods and services demanded in Country A will increase.

Relationship between price level and net exports

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The AD curve shows the relationship between price level and quantity of output demanded, holding other factors unchanged. As discussed above, when price level changes, the output level changes due to the wealth effect, interest-rate effect and exchange-rate effect. Such changes are shown by movements along an AD curve.

However, when other factors (e.g. government policy) change, and the price level remains unchanged, the whole AD curve will shift to the right or left. For example, when government increases spending on infrastructure, the AD curve will shift to the right from AD₁ to AD₂. This shift is caused by government policy, not by the changes in the price level.

Don’t Confuse!Don’t

Confuse!Don’t Confuse!

Figure 3 Shift of the AD Curve

Shift of the AD curve versus Movement along the AD curve

Price level

0 output

AD

1

P

1

AD

₂

Y

₁

Y

2

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I. Private consumption expenditure

Other things being equal, an increase in private consumption expenditure will shift the AD curve to the right and vice versa. Private consumption expenditure is mainly determined by:

(i) Disposable income (after-tax income): If the government cuts taxes e.g. salaries tax, people’s disposable income increases and they would spend more. This will result in an increase in aggregate demand.

(ii) Desire to save: If Hong Kong people become more concerned with saving for retirement and reduce current consumption, aggregate demand will decline.

(iii) Wealth (value of assets): If the Hong Kong stock market booms, people become wealthier and they tend to spend more.

(iv) Interest rate: When interest rate falls, people fi nd the costs of borrowing lower and they have higher incentive to borrow for consumption.

II. Investment expenditure

Any factors fostering fi rms to invest more would shift the AD curve to the right and vice versa. Firms’

incentives to invest are determined primarily by:

(i) Productivity of factor inputs: If fi rms fi nd new tools and machinery (e.g. a faster computer) that can increase output given the same amount of resources, fi rms are more willing to invest in the new tools and machinery.

(ii) Business prospects: Optimistic business prospects offer better returns on investment.

Business fi rms have higher incentive to invest. On the contrary, pessimistic business conditions incentivize fi rms to cut back investment spending.

2.4 Determinants of aggregate demand

As mentioned above, when the price level keeps constant, other factors may change the aggregate demand, which shifts the AD curve to the left or right. These ‘other factors’ are called the determinants of aggregate demand. Put it in another way, these determinants are the factors shifting the AD curve while keeping the price level unchanged. The factors are discussed below.

: If fi rms fi nd new tools and machinery (e.g. a faster computer) that

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(iii) Government policy: Government policy can encourage or discourage investment. For example, tax exemption for investment will motivate fi rms to invest more.

(iv) Money supply and interest rate: An increase in the supply of money lowers the interest rate in the short run. This leads to more investment spending, which causes an increase in aggregate demand.

III. Government expenditure

When government increases expenditure on infrastructure or other services such as education and medical services, this shifts the AD curve to the right and vice versa for a decrease in government expenditure.

IV. Net export

Net exports (NX) is equal to the value of exports minus the value of imports. Apart from being

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Aggregate Supply and Aggregate Demand Model 10 (i) Economic conditions of foreign countries: When the income levels of foreign countries (i.e.

trading partners) grow faster than that of domestic economy, foreign countries will buy more goods from the domestic economy and NX of domestic economy will rise. The AD curve will shift to the right. On the contrary, if the income level of domestic economy grows faster than that of foreign countries, domestic economy will import more and export less. NX will fall and the AD curve will shift to the left.

(ii) Exchange rate: NX will fall when the value of domestic currency rises against foreign currency.

To illustrate, if the exchange rate between euro and U.S.$ changes from €1 = U.S.$1.5 to €1 = U.S.$1.7, the value of euro increases and the prices of European products in the U.S. will rise, which makes European goods less competitive in the U.S. market. The NX of European countries will fall and the AD curve will shift to the left. By the same analysis, a decrease in value of domestic currency will make domestically produced goods more competitive in the overseas market. It will shift the AD curve to the right.

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Don’t Confuse!Don’t

Confuse!Don’t Confuse!

The AD curve in Macroeconomics shows the relationship between price level and aggregate quantity of output demanded, holding all other factors unchanged.

As discussed above, when price level changes, the aggregate quantity of output demanded changes due to the wealth effect, interest-rate effect and exchange-rate effect.

The demand curve in Microeconomics also slopes downward, but the reasons are not the same as those for the AD curve in Macroeconomics. The demand curve of a good in Microeconomics slopes downward because when the price of the good goes down, the purchasing power of the consumer goes up and they are willing and able to buy more of that good. This is income effect. At the same time, the fall in price of the good makes it relatively cheaper given prices of other goods remain unchanged.

The consumer will buy more of the cheaper good. This is substitution effect.

The demand curve in Microeconomics is for a single good, so there can be substitution effect when the price of that good changes. However, the AD curve in Macroeconomics depicts the relationship of general price level and aggregate output level (i.e. all goods and services produced). A rise in general price level means that the prices of all domestically produced goods and services rise. Consumers have no other goods and services which they can substitute for. There is no substitution effect for AD curve in Macroeconomics.

AD curve in Macroeconomics and Demand Curve in Microeconomics

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3 Aggregate Supply

3.1 What is aggregate supply?

Aggregate supply (AS) refers to the total amount of goods and services supplied by the fi rms in an economy.

3.2 What is an aggregate supply curve?

The aggregate supply (AS) curve shows the relationship between price level and the quantity of output that fi rms in an economy are willing and able to supply.

It must be noted that since the effects of changes in price level on aggregate supply is very different in short run and long run, we will use two AS curves i.e. the short run aggregate supply (SRAS) curve and the long run aggregate supply (LRAS) curve, for our analysis. We will fi rst examine the long run aggregate supply curve.

3.3 Why is the long run aggregate supply curve vertical?

In the long run, an economy’s production of goods and services depends on its availability of resources i.e. labour, capital and natural resources along with the available production technology. In other words, we can say that our long run production capacity is constrained by the available resources and

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Figure 4 Long run aggregate supply curve

technology. Then we can further infer that price will have no effects on output level in the long run because the change of price level will not change the amount of resources and technology available in the economy. Because the price level does not affect the determinants of output in the long run, the long-run aggregate-supply curve is vertical.

Price level

0 Output

LRAS

Full-employment output/Natural Rate of Output

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Aggregate Supply and Aggregate Demand Model 14 Knowledge

Enrichment Knowledge EnrichmentKnowledge Enrichment

3.4 What are the factors shifting LRAS curve?

The position of the LRAS is at an output level which sometimes is referred to as potential output or full-employment output. This is the level of output that the economy produces when resources are fully utilised (i.e. fi rms produce at their full capacity) and the economy is at the full-employment level ( i.e. the employment level that all people who want to fi nd a job will have one, except those structurally and frictionally unemployed, that is the natural rate of unemployment¹.). This level of output is also called natural rate of output.

1 Natural rate of unemployment is not required in the Curriculum.

Structural unemployment refers to the unemployment caused by the mismatch of the skills and attributes of workers and the requirements of the jobs.

Frictional unemployment refers to the short-term unemployment arising from the time and process of matching job-seekers and the jobs available.

Please note that when we say the economy is operating at the full-employment level, it does not mean the unemployment rate is zero in the economy, there is still structural and frictional unemployment.

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Based on the above discussion, it follows that any factors, which can change the natural rate of output, will shift the LRAS curve. The following four factors are able to change the production capacity of an economy, which in turn shifts the LRAS curve.

(i) Labour: Labour supply can be increased by growth in population, increases in immigrants, and a fall in the natural rate of unemployment. The long-run aggregate-supply curve would then shift to the right.

(ii) Capital: Capital includes both physical and human capital. An increase in the economy’s physical capital stock (e.g. factories, machinery and tools) raises productivity and thus shifts the LRAS curve to the right. The rightward shift of LRAS curve can also be accomplished by an increase in human capital (e.g. skills and knowledge of the workers).

(iii) Natural Resources: A discovery of new minerals and natural resources increases long run aggregate supply. On the contrary, a change in weather patterns e.g. more frequent drought or fl oods that makes farming more diffi cult and hence shifts LRAS curve to the left.

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Aggregate Supply and Aggregate Demand Model 16 (iv) Technological Knowledge: Technological change refers to an advance in knowledge which

improves ways to produce goods and services, that is to improve the production effi ciency of goods and services. For example, the invention of computer has allowed us to produce more goods and services from any given level of resources. As a result, it has shifted the LRAS curve to the right.

3.5 Why is the short run aggregate supply curve upward sloping?

The LRAS curve is vertical because price level has no effect on output in the long run. However, the SRAS curve is upward sloping, which indicates that an increase in the overall price level tends to raise the quantity of goods and services supplied and a decrease in the overall price level tends to lower the quantity of goods and services supplied in the economy. Why is there a positive relationship between price and output levels in the short run? The clue lies on the absence of capacity constraints and the imperfect adjustment of input and output prices².

2 Starting from S4 in 2013/14, i.e.2016 HKDSE Examination, students are expected to grasp “imperfect adjustment of input and output prices” as the ONLY explanation required for an upward-sloping SRAS curve.

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3.5.1 Absence of capacity constraints

In Figure 5, the full production capacity point is Point D. Suppose the economy is not producing in full capacity (i.e. point D) in the short run but producing at a low level of output (e.g. point A). It means that there is excess capacity (i.e. no capacity constraints) in either individual fi rms or in the whole economy. There are unemployed resources/factor inputs (labour, capital and so on) available in the economy. When there is a rise in aggregate demand, the proportion of increase in output is greater than that in price (from point A to point B). This can be achieved because fi rms can recruit the originally unemployed factor inputs whose prices do not increase much. Therefore, the SRAS curve is relatively fl atter in this portion.

However, when output continues to expand the economy would move closer to full capacity (point D). The number of unemployed factor inputs will be falling and their prices will begin to rise rapidly.

Therefore, the proportion of increase in output price will be larger than that in output quantity. The SRAS curve becomes much steeper (i.e. the portion between point C and point D).

3.5.2 Imperfect adjustment of input and output prices

The above exposition shows that when the economy is producing below full capacity, the SRAS curve is upward sloping, whether or not it is fl at or steep. However, excess production capacity itself cannot fully explain why SRAS is upward sloping. Imagine that if factor prices rise at the same pace as output prices, fi rms have no incentive to produce more as they make no additional profi t, the SRAS curve will become vertical, like the LRAS. For example, if a 10% increase in output prices is immediately matched by a 10% increase in factor costs, the profi ts for the fi rms remain unchanged and they have no incentive to increase any output.

However, in reality, adjustments in input prices always lag behind changes in product prices. It is particularly true when wage contracts are signed the wage rates remain unchanged even when product prices change. It also applies to capital goods or other raw materials, the purchase prices are agreed well before the changes in product prices. In this case, factor input prices tend to adjust slowly to the changes in overall output prices. The imperfect adjustment of input and output prices incentivizes the fi rms to increase output when output prices rise to capture additional profi t. This also applies to the case that when output prices fall, the input prices do not fall at the same pace, the imperfect adjustment of input and output prices incentivizes the fi rms to reduce output to minimize losses.

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Aggregate Supply and Aggregate Demand Model 18 Figure 5 Short run aggregate supply (SRAS) curve

The above exposition provides a general explanation of why the SRAS curve is upward sloping.

However, to be more specifi c, there are three theories put forward to explain this relationship.

I. The Sticky-Wage Theory

Nominal wages are often slow to adjust in the economy due to long-term contracts between workers and fi rms. Since wages do not immediately adjust to the price level, an increase in price level makes employment and production more profi table, leading fi rms to increase the quantity of goods and services supplied.

produce more if they are willing to do so. Imperfect adjustment of input and output prices gives an incentive for fi rms to increase (decrease) output when output prices increase (decrease).

Price level

0 Output

SRAS

A B

C D

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For instance, suppose a fi rm has agreed in advance a certain amount of wage to be paid to workers but then the price level increases unexpectedly. This implies that the fi rm is now paying a real wage (wage/price level) that is lower than it intended and its profi t rises. Thus, the fi rm hires more labor and produces a greater quantity of goods and services.

II. The Sticky-Price Theory

The prices of some goods and services are also sometimes slow to respond to changes in the economy because of the costs of adjusting prices which are named as menu costs. Menu costs include the costs of printing new menu and catalog as well as the time involved. If the price level rises unexpectedly, some fi rms immediately adjust their prices upward, but there are fi rms which do not change the price of their products quickly. It may be due to the fact that these fi rms would like to temporarily avoid the menu costs. The price of their products will be relatively lower and this will lead to a profi t in sales.

Thus, when sales increase, fi rms will produce more quantity of goods and services. In a word, because not all prices adjust instantly to changing conditions, an unexpected rise in the price level leaves some fi rms charging with relatively lower prices, which would boost sales and cause fi rms to increase the quantity of goods and services supplied.

III. The Misperception Theory

Changes in the price level can temporarily mislead suppliers about what is happening in the market in which they sell their output. As a result of these misperceptions, suppliers respond to changes in

Employment

Contract

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Aggregate Supply and Aggregate Demand Model 20 Don’t

Confuse!

Don’t Confuse!Don’t Confuse!

Please note that according to the Sticky- Price Theory, the SRAS curve is upward sloping because some suppliers are slow to respond to the change of general price level to avoid the menu cost temporarily.

However, the Misperception Theory explains that some suppliers over-respond to the change of general price level due to the lack of information.

The Sticky-Price Theory and the Misperception Theory

To explain the theory in a more concrete way, suppose that the general price level rises unexpectedly.

Some fi rms mistakenly believe that the price of their products rises and they perceive it as an increase in the relative price of their products. Firms may then believe that the reward of supplying their product has increased, and thus they increase the quantity that they supply. A higher general price level causes misperceptions about relative prices, and these misperceptions lead fi rms to respond to the higher price level by increasing the quantity of goods and services supplied.

MENU

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3.6 What are the factors shifting the short run aggregate supply curve?

Factors that shift the LRAS curve will also shift the SRAS curve. However, people’s expectation of the price level will affect the position of the SRAS curve even though it has no effect on the LRAS curve.

A higher expected price level decreases the quantity of goods and services supplied and shifts the SRAS curve to the left. Suppose workers and fi rms expect the future price will increase, the workers will negotiate a rise in wage to maintain their purchasing power and fi rms facing higher factor prices will raise the output prices accordingly. If all fi rms and workers in the economy are affected by higher expected prices, the costs of production will increase and the SRAS curve will shift to the left. By the same analysis, a lower expected price level increases the quantity of goods and services supplied and shifts the SRAS curve to the right.

3.7 Concluding remark

In the short run, not all prices, including prices of factor inputs (e.g. wages), adjust at the same pace.

Therefore, when price level goes up, fi rms are willing to supply more goods and services because profi ts are higher. As a result, the SRAS curve is upward-sloping. However, in the long run, all prices, including prices of factor inputs, are fully (or completely) adjusted. The three percent change in price level will be accompanied by three percent change in factor prices. Any increase in profi ts is absorbed by the rise of input prices, so the fi rm will have no incentive to increase the supply of goods and services. It follows that change in price level will have no effect on aggregate supply in the long run.

The LRAS curve is thus vertical.

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4.1 Determinants of equilibrium output and price levels in the long run

Long run equilibrium is found where the aggregate demand curve intersects with the long run aggregate supply curve. Output is at its natural rate. Also at this point, perceptions, factor prices, and prices have fully adjusted and resources are utilized at its full capacity. Therefore, the SRAS curve and AD curve intersect at the potential (i.e. full employment) output level.

4 Determination of the Equilibrium Levels of Output and Price in the AS- AD Model

Price level

0 Output

LRAS

Y_f

SRAS

AD P*

Figure 6 Long run equilibrium

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4.2 Changes in equilibrium levels of price and output

Any changes in AD and SRAS will result in changes in price and output levels in the short run.

However, the automatic adjustment mechanism in the market can restore the economy back to long run equilibrium. We will start our analysis with a change in AD.

I. The effects of a change in aggregate demand

Figure 7 The effects of a shift in AD curve

Suppose households and fi rms are pessimistic about the future economic conditions, which causes

SRAS

1

AD

₁

Price level

0 Output

LRAS

Y

f

P

₁

SRAS

₂

AD

₂

A

C P

2

B

P

₃

Y₂

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Aggregate Supply and Aggregate Demand Model 24 It is not uncommon for the government to eliminate the recession by boosting government spending.

By doing so, aggregate demand curve shifts back to the right. The equilibrium moves back from B to A.

However, even if the government does nothing, it is possible that the economy will eventually move back to the full-employment output level. As shown in Figure 7, under recession, price level falls from P₁ to P₂. Workers and fi rms are willing to adjust their sticky wages and sticky prices. When output is low, unemployment is high. Workers are now willing to accept lower wages and fi rms are willing to accept lower prices. After all adjustments, the SRAS curve shifts to the right, from SRAS₁ to SRAS₂. Equilibrium moves from B to C, reaching again the full-employment output level at a lower price level P₃. The process of adjustment back to the full-employment output level is called automatic adjustment mechanism.

In the long run, the decrease in aggregate demand causes a drop in the equilibrium price level but leave the output level unchanged. Thus, the long-run effect of a change in aggregate demand is a nominal change (in the price level) but not a real change (output level remains constant) .

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Figure 8 The effects of a shift in SRAS curve Y₂

SRAS

₁

AD

₁

SRAS

2

Price level

0 Output

LRAS

Y

f

P

₁

A

P

₂

B

caused by automatic adjustment mechanism

Suppose fi rms face a sudden increase in their costs of production (e.g. oil price increases substantially).

This will cause the SRAS curve to shift to the left (SRAS₁ to SRAS₂ in Figure 8). Assume that it does not affect the LRAS. In the short run, output will fall and the price level will rise, this situation is called stagfl ation (i.e. a period of falling output and rising prices). The equilibrium moves from A to B.

II. The effects of a change in short run aggregate supply curve

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Aggregate Supply and Aggregate Demand Model 26 If the government does nothing, price

and wage expectations will adjust. With increased unemployment caused by recession, workers are willing to accept lower wages. When nominal wages fall, producing goods and services becomes more profi table and fi rms are able and willing to supply more, causing the SRAS curve to shift back to the right. Recession gradually ends and employment rebounds.

The equilibrium moves back from B to A (SRAS₂ to SRAS₁).

However, if the government is impatient to wait for the automatic adjustment

mechanism (the impatience of the government may be due to political pressure), it can shift the AD curve by increasing government expenditure. AD curve shifts from AD₁ to AD₂ (Figure 9). The recession will end, but the price level will be permanently higher at P₃. The higher price level is pushed by the government’s expansionary fi scal policy. The equilibrium moves from A to B, and then fi nally to C.

Shop Shop

Shop Shop Shop Shop

stagflation

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Figure 9 Government increases expenditure to reduce the impacts of stagfl ation

SRAS

2

AD

2

Price level

0 Output

LRAS

Y

f

P

3

SRAS

1

AD

1

C A P

2

B

P

1

Y₂

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Aggregate Supply and Aggregate Demand Model 28 Hints

Hints Hints

It is not diffi cult to use the AS-AD model to analyse changes in price and output levels in the short run if students are able to follow the four steps:

1 Determine whether the AD or SRAS curve would shift caused by the event.

2 Determine whether the curve concerned shifts to the left or right.

3 Use an AD-AS diagram to see how the shift changes output and price levels in the short run.

4 Use an AD-AS diagram to see how economy moves from the new short run equilibrium to the new long run equilibrium.

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5.1 Highlights of the Budget 2014-15

Forecast GDP growth is 3–4%.

Average rate of headline infl ation for the year is estimated at 4.6%.

Government expenditure is estimated to reach $411.2 billion;

total government revenue is estimated to be $430.1 billion.

Major policy areas include enhance competitiveness and manpower and increase land supply.

Please refer to http://www.budget.gov.hk/2014/eng/highlights.

html for further details.

5 Application of the AS-AD Model: The

Case of the Budget 2014-15

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5.2 How does the Budget affect our macroeconomy?

In terms of the impacts on the AS and AD, the expenditure items highlighted in the Budget can be subdivided into the following three categories:

The fi rst category includes the expenditure items having less prominent effects on both AS and AD as the amount of expenditure is relatively limited. The expenditures on health care of this Budget fall on this category. They have relatively slight impact on AD.

The second category of expenditure items will have more signifi cant effects on price and output in the short run, but less in the long run. The social welfare and relief measure belong to this category. These expenditure items are more substantial and consumptive in nature, which means that they increase the AD in the short run, but not much effect on the long run. These policies shift the AD curve to the right, both price and output levels will rise in the short run. Since the expenditures do not change the available factor inputs and the production capacity is not much affected, there will be limited effects on LRAS.

The third category includes expenditures having more signifi cant effects on price and output in both the short run and the long run. Education and increase in land supply are two major policies under this category.

I. Case of education

Take education as an example. Refer to Figure 10. Suppose the initial output level is below the full employment output level. If the original equilibrium is at A, increase in education expenditure shifts AD₁ to AD. The new equilibrium is at B and the economy reaches its full employment output level.

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Figure 10 The effects of an increase in education expenditure

However, if the original equilibrium has already been at the full employment level (Point B), the increase in education expenditure will shift AD to AD₂. Output increases from Y_f to Y₂. Prices go up to P₂ and workers will bargain for higher wage to maintain their purchasing power. SRAS curve will shift to the left and reach the equilibrium point D, resulting in an even higher price level, but restoring the output level back to Y_f.

P

₂

Y₁

C

SRAS

AD Price level

0 Output

LRAS

Y

f

P

₃

AD

₁

B

A

P AD

₂

D

Y₂

P

₁

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Aggregate Supply and Aggregate Demand Model 32 Nevertheless, education will increase human capital which increases production capacity of the economy. The LRAS curve will shift to the right. If long run output can be increased to Y₂, price level will fall back to P₂. Here, we draw an important conclusion: any rightward shift in AD will push up prices in the short run, but the extent of price increase will be smaller if output level can be increased in the long run (i.e. a rightward shift of LRAS curve). (See Figure 11)

II. Case of land supply

Figure 11 can be used to illustrate the case of increasing land supply. Land supply increases expand the production capacity of the economy. LRAS curve shifts from LRAS₂₀₁₄ to LRAS₂₀₁₆. Prices will fall substantially if AD remains unchanged at AD₂₀₁₄. However, AD is not constant and it increases over time. Though price level goes up, the extent is smaller than that under fi xed long run output level.

Figure 11 The effects of an increase in land supply

P

₂₀₁₆

Y₂₀₁₄

AD

₂₀₁₆

AD

₂₀₁₄

AD

2019

Y₂₀₁₉

Price level

0 Output

LRAS

₂₀₁₆

Y

2016

LRAS

₂₀₁₉

LRAS

₂₀₁₄

P

2019

P

2014

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edition, Pearson, Chapter 24.

Mankiw, N. G. (2012), Principles of Economics, 6^th edition, South-Western, CENGAGE Learning, Chapter 33.

O’Sullivan, A., Sheffrin, S. M. and Perez, S. J. (2008) Economics: Principles, Applications and Tools, 5^th edition, Pearson, Chapter 9.

The 2014-15 Budget, The Government of the Hong Kong Special Administrative Region

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National Income Determination and Price Level:

Aggregate Supply and Aggregate Demand Model

Resource Pack for the Economics Curriculum (Secondary 4-6)

Personal, Social and Humanities Education Section Curriculum Development Institute Education Bureau 2014

Schools may make copies for educational purpose.

National Income Determination and Price Level:

Aggregate Supply and Aggregate Demand Model

Resource Pack for the Economics Curriculum (Secondary 4-6)

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