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Aggregate demand and aggregate supply

Wealth, income and inequality

What does it mean to be wealthy? The answer to this question varies from culture to culture. In the modernised, industrial world that we live in, wealth generally means all the collected store of valuable things that belong to a person (or family, company or country). Wealth can include money saved in bank accounts, or invested in pension schemes. It can include land, houses or other property and valuable belongings such as works of art or precious jewels. Many people also own stocks and shares in companies. The various things that make up a person's wealth are often called assets.

So wealth is a static thing. The term income, on the other hand, suggests a flow of money. Income is the amount of money that a person (or family or company) receives over a period of time. For most people, this means the salary they get for the work they do. However, there are other sources of income. One source is government benefits, such as unemployment benefit or family support. Another source is rent from property and another is interest from savings.

Huge inequalities in wealth owned by individuals exist in many countries. Take the United Kingdom for example. A fifth of all the marketable wealth is owned by just one per cent of the UK's population. That one per cent own over £355 billion of assets. Figure 1 on page 56 shows how the rest of the United Kingdom's wealth is distributed. As you can see, the richest 50 per cent of the population own over 93 per cent of the wealth. In other words, half the population own nearly all the wealth and the other half own only a tiny percentage. The chart also shows that the richest one per cent of the population own over a fifth of all the country's wealth.

Large inequalities also exist in the distribution of income. The extent of these inequalities can be shown with something called the Lorenz curve. You can see an example in figure 2 below. The straight blue line shows perfectly equal distribution of income. For example, the bottom 20 per cent earn 20 per cent of the total income. The bottom 40 per cent earn 40 per cent and so on. This is the ideal situation. The red curve, however, shows the real situation for the United Kingdom. You can see immediately how far from perfect the distribution is. Half of the population, for example, earn just under a third of the total income. Move horizontally along the population line and you can see that 90 per cent of the population take only 70 per cent of the total income. This means that the top ten per cent of the population earn nearly 30 per cent of the country's total income.


Without a doubt poverty is a huge problem in the world today. Figures suggest that three billion people or half the world's population live in poverty. However, although we associate poverty with developing countries, poverty of some kind also exists in industrialised nations. For example, it is now thought that quite possibly one in every ten Americans lives in poverty. However, poverty means different things to different people. How do economists define poverty?

One measure of poverty is absolute poverty. People live in absolute poverty when they live on or below the poverty line. This is a level of income that is so low that people cannot afford the basic necessities to live, such as food, clothing and shelter. According to the World Bank, these are people who are living on two dollars a day.

However, there are one billion people in the world who live on less than one dollar a day. The World Bank defines this as extreme poverty.

Few people in industrialised countries live in absolute poverty, but many live in relative poverty. This measure of poverty takes into account the differences that exist in a population between the rich and the poor. For example, some economists say that people who earn less than half the average income live in relative poverty. In Britain, this means 14 million people.

Why does poverty still exist? There is no single answer to this question. In developing countries, causes of absolute poverty include natural disasters like droughts and floods, political corruption and war. However, in many cases people - and whole populations - are caught in a trap: the poverty trap.

People on a low income spend everything they have on daily necessities. They save almost nothing. In order to raise themselves out of poverty, they need education. This costs money. Even when governments provide free schooling, the poor may not send their children because they need them to work. These families cannot afford the cost of sending a child to school. Without education, the children cannot find better paid work. In this way, generations of the same family remain poor.

The same cycle that traps individuals can trap a whole population. Economic growth depends on investment. Investment money comes from savings. A nation that has almost no savings cannot grow economically. This keeps wages low, so again people cannot save and the cycle continues.


In the 1930s one of the world's strongest economies suffered a devastating collapse. It was the American economy, and the disaster was the Great Depression. The effects of the Great Depression were felt all around the world, and it brought about a change in economic thinking. Economists began to realise that looking at the behaviour of individual consumers and suppliers in the economy was not enough. Economists and governments had to understand how the whole economy worked. In other words, they had to have an understanding of macroeconomics.

Microeconomics looks at how the details of the economy work. Macroeconomics takes a few steps back and looks at the whole picture. While microeconomics looks at supply and demand for a single product or industry, macroeconomics follows supply and demand patterns for the whole economy. Whereas microeconomics is about economic events at home, macroeconomics looks at how the domestic economy interacts with the economics of other countries.

However, macroeconomics isn't only about knowing what's happening in the economy. After the shock of the Great Depression, governments realised that an economy needs to be managed. Most governments aim to have steady economic growth, to control inflation and to avoid recessions. Just managing an individual business is a hard enough task. How do you manage a whole economy? Governments have certain mechanisms which help them to do this.

The first of these mechanisms is fiscal policy. Fiscal policy refers to the tax system and to government spending. By increasing or decreasing the amount of tax people must pay, the government can affect how much money people have available to spend (disposable income). This, in turn, has an effect on demand in the market. By increasing or decreasing their own spending, governments can have a huge effect on the growth of the economy.

The second mechanism is monetary policy. With its monetary policy, a government sets interest rates and also controls the amount of money that circulates in the economy. The interest rate the government sets influences the rate that commercial banks set when they lend money to customers. Interest rates have a big impact on the economy. For example, they can affect people's decisions about saving or spending money.

The third mechanism is administrative approach. This is a range of things that governments do to increase the supply of goods and services to the economy but without increasing prices. There are a number of ways governments try to do this. For example, improvements in education and training can make the workforce more productive. Investment in technology can make industry more efficient. Governments can also change employment and business laws to make the market more competitive.

With a combination of these methods, governments try to steer or guide the economy on a steady and predictable path. They aim for gradual economic growth and to avoid disasters like the Great Depression.

Aggregate demand and aggregate supply

When a company makes plans for how much to produce and what prices to set, it needs information. The company needs to predict the level of supply that will be required to meet demand. It needs to set prices that will keep the business running. In the same way, governments need this information for the whole economy. The total level of demand for all products and services is called the aggregate demand. The total supply is called the aggregate supply.

The demand for products and services is how much is wanted. For a company, the demand comes from customers. For a whole economy, things are a little more complicated. Demand in the whole economy comes from the following:

- from consumers, because they buy products and services (consumption)

- from companies, because they invest money to build factories and buy machines (investment)

- from the government, because they spend money on services and projects (government spending)

- from exports, because these are sales to customers in other countries (export)

Although aggregate demand is made up of many things, it behaves in the same way as demand for a single product. For example, demand rises when incomes rise. The same applies to aggregate demand. Similarly, demand falls as prices rise. The same is true for aggregate demand. You can see this relationship shown in figure 1 on page 63. The vertical axis shows prices. The horizontal axis shows real national income. Real national income is the value of all the services and products produced by the whole economy. It's calculated in the same way as aggregate demand (consumption, investment, government spending and exports). You can sec from the curve that national income (and therefore aggregate demand) increases as prices fall.

Changes in any of the four things which make up aggregate demand will cause a shift in demand. For example, if the government decides to spend a huge amount of money on building new hospitals and schools, this will have an effect on the whole economy. Aggregate demand will increase at all price levels. This is shown in aggregate demand curve 2 (AD2) in figure 1.

The supply curve for an individual product or service is very simple. As the company increases its supply to the market, it increases the price. But what about aggregate supply for the whole economy? This is more complex. In the short run, aggregate supply follows the same trend as the supply for a single product. Supply rises as prices rise. However, the long run is different. In the long run, supply is not affected by price. In the long run, production is limited by the factors of production. In other words, what a country can supply depends on the number of factories it has, the number of people working and the availability of raw materials. This is why the long run supply curve in figure 2 on page 63 is a straight line.



The cash we use every day is something we take for granted, but for thousands of years people traded without it. Before money was invented, people used a system called bartering. Bartering is simply swapping one good for another. Imagine that you have milk, for example, and you want eggs. You simply find someone who has eggs and wants milk - and you swap! However, you can see that this isn't a very convenient way to trade.

First of all, you can't be sure that anyone will want what you've got to offer. You have to hope that you'll be lucky and find someone who has what you want and that he or she wants what you've got. The second problem with bartering is that many goods don't hold their value. For example, you can't keep your milk for a few months and then barter it. Nobody will want it!

After some time, people realised that some goods held their value and were easy to carry around and to trade with. Examples were metals like copper, bronze and gold and other useful goods like salt. These are examples of commodity money.

With commodity money, the thing used for buying goods has inherent value. For example, gold has inherent value because it is rare, beautiful and useful. Salt has inherent value because it makes food tasty. If you could buy things with a bag of salt, it meant you could keep a store of salt and buy things anytime you needed them. In other words, commodity money can store value.

Using commodity money was much more convenient than ordinary bartering, but it still had drawbacks. One of these drawbacks is that commodity money often lacks liquidity. Liquidity refers to how easily money can circulate. There is obviously a limit to how much salt you can carry around! There's another problem with commodity money: not everyone may agree on the value of the commodity which is used as money. If you live by the sea, salt may not be so valuable to you. Money needs to be a good unit of account. In other words, everyone should know and agree on the value of a unit. This way, money can be used to measure the value of other things.

The solution is to create a kind of money that does not have any real intrinsic value, but that represents value. This is called fiat money. The coins and notes that we use today are an example of fiat money. Notes don't have any inherent value - they are just paper. However, everyone agrees that they are worth something. More importantly, their value is guaranteed by the government. This is the reason why pounds and dollars and the world's other currencies have value.


If you work, you've probably got a bank account. You could keep the money you earn each month in a box under your bed, but it wouldn't be very sensible. One reason is that it's not very safe. If your house gets burgled, you'll lose everything you've saved. Another reason is that your money will lose value.

As prices rise, the money in a box under your bed will be able to buy fewer and fewer things. Money in a bank savings account, however, will earn interest. The interest will help compensate for the effect of inflation. But banks are more than just safe places for your money. What other services do they offer?

The other main service is lending money. Individuals and businesses often need to borrow money, and they need a lender that they can trust. This is exactly what banks are - reliable lenders. In fact, most of the money that people deposit in their bank accounts is immediately lent out to someone else.

Apart from storing and lending money, banks offer other financial services. Most of these are ways of making money more accessible to customers. For example, banks help people transfer money securely. They give customers cheque books and credit cards to use instead of cash. They provide ATM machines so that people can get cash any time of the day or night.

But how do banks make a living? Basically, they make a living by charging interest on loans. Of course, when you make a deposit into a bank savings account, the bank pays you interest on that money. However, the rate they pay savers is less than the rate they charge borrowers. The extra money they make by charging interest on loans is where banks earn most of their money.

For banks, interest is also a kind of security. Sometimes people do not pay back money they borrow. This is called defaulting on a loan. When someone defaults on a loan, the bank uses money earned from interest to cover the loss.

All of this means that most of the money people have saved in the bank is not there at all! A small amount of the total savings is kept by the bank so that customers can make withdrawals. The rest, however, is made available for loans. The amount that is kept is called the reserve. The reserve must be a certain percentage of all the savings received from customers - for example 20 per cent. This figure is set by the central bank, and this is one of the ways that governments can control the amount of money circulating in the economy.


Fiscal policy

As we saw in unit 12, fiscal policy is one of the tools that governments have to keep the economy on a steady path. The two main components of fiscal policy arc changes to the tax system and changes in government spending. But what changes can governments make in these two areas, and how do changes affect the growth of the economy?

Let's look first at the tax system, and in particular at income tax. Income tax is one of the biggest sources of income for a government. Many governments operate a system called progressive taxation. This means that the more you earn, the more tax you pay. People are usually allowed to keep some of their income without paying any tax. This is called the personal allowance. The rest of their income is then taxed using the progressive system. For example:


Income Personal Tax to pay

before tax allowance after allowance

£0-£1,999 10%

£2,000 - £29,999 £5,000 22%

£30,000 and over 40%


Governments can decide to change the size of the personal allowance, or change the percentage that each income group has to pay. If the economy is growing too fast, and demand for goods and services is more than the economy can supply, the government will want to slow down spending.

To do this, they can decrease the personal allowance, or they can increase the percentage to pay in tax. This will mean people have less disposable income, and spending will slow down. If the economy is slowing down too much, governments can do the opposite.

What about government spending? How does that affect economic growth? The key to this is something called the multiplier effect. To understand how this works, let's look at an example. Imagine that the economy is not growing. This will make aggregate demand fall. In turn, productivity falls. This situation means that the nation's resources are not all being used. In other words, there are surplus raw materials, machines are not being used and workers are unemployed. What the economy needs is a pull in demand for goods and services.

The government can provide this pull by spending a large amount of money on public projects. For example, imagine that the transport department decides to spend £200 million on building a new motorway. This will give work to building companies and jobs to unemployed workers. In other words, more resources are being used and the nation's productivity is increased.

Companies and workers on the motorway project will save some of the money they earn, but also spend some. The money they spend will be income for others in the economy. If half of the £200 million is spent, then the total national income has grown by this much:

£200 million + (0.5 x £200 million)

Each time a proportion of the income is passed on, the economy grows again:

£200 million + (0.5 x £200 million) + (0.5 x £100 million), etc.

In theory, the multiplier effect will continue until there is full employment and the nation's resources are being used to their fullest extent.

Monetary policy

Monetary policy is another tool that governments use to control the economy. Monetary policy mainly involves making changes to the interest rate. It can also involve changing the amount of money that circulates round the economy. However, this second kind of monetary policy isn't used very often because it can lead to inflation. Changing interest rates, on the other hand, is a method that is used quite frequently for slowing down or speeding up the economy. So how does it work?

Basically, commercial banks - the ones that you and I use to keep our savings in and to borrow from - borrow their money from the country's central bank. This is the national or government bank, and it has the power to set interest rates. The interest rate of the central bank will influence the rates commercial banks set for their customers. When interest rates go up, borrowing money becomes more expensive. When they go down, it becomes cheaper.

People get loans from banks for all sorts of reasons, but the biggest loan most people take out is to buy a house. This kind of loan is called a mortgage. When interest rates increase, mortgages become more expensive. People who already have a mortgage will need to pay more on their repayments, and will have less money to spend on other things. Fewer people will want to buy new houses and house prices will fall.

In turn, home owners will feel less confident about their own wealth and will spend less. As a result, the economy slows down. A fall in interest rates will have the opposite effect on the house buying chain.

Consumers also buy other things using borrowed money. This is called buying on credit, and interest rates will also affect how much people spend on credit. Purchases made using credit cards are now a huge proportion of total spending in many countries. This means that interest rate changes have a big impact on consumer spending and the economy as a whole.

Companies, too, are affected by interest rate changes. When interest rates are low, they feel more confident about investing in order to expand their business. Low interest rates will encourage them to take out loans in order to build factories, buy machines and increase production. All of this increases the size of national output. Again, higher interest rates will have the opposite effect.

Finally, interest rates can have an effect on the amount of exports a country sells. This is because the value of a currency (the exchange rate) often falls when the interest rate falls. When the value of a currency falls, a nation's products and services become cheaper for customers from other countries. This increases export sales, and more money comes into the economy. And, of course, a rise in interest rates will mean a rise in the exchange rate. This will reduce export sales, and reduce the total output of the economy.

Date: 2015-12-11; view: 7923

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