Labour economics seeks to understand the functioning of the market and dynamics for labour. Labour markets function through the interaction of workers and employers. Labour economics looks at the suppliers of labour services (workers), the demanders of labour services (employers), and attempts to understand the resulting pattern of wages, employment, and income.

It is an important subject because unemployment is a problem that affects the public most directly and severely. Full employment (or reduced unemployment) is a goal of many modern governments.

Two ways of analysing labour markets

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There are two sides to labour economics. Labour economics can generally be seen as the application of microeconomic or macroeconomic techniques to the labour market. Microeconomic techniques study the role of individuals in the labour market. Macroeconomic techniques look at the interrelations between the labour market, the goods market, the money market, and the foreign trade market. It looks at how these interactions influence macro variables such as employment levels, participation rates, aggregate income and Gross Domestic Product.

The macroeconomics of labour markets

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The labour force is defined as the number of people employed plus the number unemployed but seeking work. The participation rate is the number of people in the labour force divided by the size of the adult population (or by the population of working age). The unemployment level is defined as the labour force minus the number of people currently employed. The unemployment rate is defined as the level of unemployment divided by the labour force. The employment rate is defined as the number of people currently employed divided by the adult population (or by the population of working age). In these statistics, self-employed people are counted as employed.

Variables like employment level, unemployment level, labour force, and unfilled vacancies are called stock variables because they measure a quantity at a point in time. They can be contrasted with flow variables which measure a quantity over a duration of time. Changes in the labour force are due to flow variables such as natural population growth, net immigration, new entrants, and retirements from the labour force. Changes in unemployment depend on: inflows made up of non-employed people starting to look for jobs and of employed people who lose their jobs and look for new ones; and outflows of people who find new employment and of people who stop looking for employment.

When looking at the overall macroeconomy, several types of unemployment have been identified, including:

• Frictional unemployment — This reflects the fact that it takes time for people to find and settle into new jobs. If 12 individuals each take one month before they start a new job, the aggregate unemployment statistics will record this as a single unemployed worker. Technological change often reduces frictional unemployment, for example: the internet made job searches cheaper and more comprehensive.
• Structural unemployment — This reflects a mismatch between the skills and other attributes of the labour force and those demanded by employers. If 4 workers each take six months off to re-train before they start a new job, the aggregate unemployment statistics will record this as two unemployed workers. Technological change often increases structural unemployment, for example: technological change might require workers to re-train.
• Natural rate of unemployment — This is the summation of frictional and structural unemployment. It is the lowest rate of unemployment that a stable economy can expect to achieve, seeing as some frictional and structural unemployment is inevitable. Economists do not agree on the natural rate, with estimates ranging from 1% to 5%, or on its meaning — some associate it with "non-accelerating inflation". The estimated rate varies from country to country and from time to time.
• Demand deficient unemployment — In Keynesian economics, any level of unemployment beyond the natural rate is most likely due to insufficient demand in the overall economy. During a recession, aggregate expenditure is deficient causing the underutilization of inputs (including labour). Aggregate expenditure (AE) can be increased, according to Keynes, by increasing consumption spending (C), increasing investment spending (I), increasing government spending (G), or increasing the net of exports minus imports (X−M).
  {AE = C + I + G + (X−M)}

The classical microeconomics of labour markets

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Economists see the labour market as similar to any other market in that the forces of supply and demand jointly determine price (in this case the wage rate) and quantity (in this case the number of people employed).

However, the labour market differs from other markets (like the markets for goods or the money market) in several ways. Perhaps the most important of these differences is the function of supply and demand in setting price and quantity. In markets for goods, if the price is high there is a tendency in the long run for more goods to be produced until the demand is satisfied. With labour, overall supply cannot effectively be manufactured because people have a limited amount of time in the day, and people are not manufactured. A rise in overall wages will, in many situations, not result in more supply of labour: it may result in less supply of labour as workers take more time off to spend their increased wages, or it may result in no change in supply. Within the overall labour market, particular segments are thought to be subject to more normal rules of supply and demand as workers are likely to change job types in response to differing wage rates.

Many economists have thought that, in the absence of laws or organizations such as unions or large multinational corporations, labour markets can be close to perfectly competitive in the economic sense — that is, there are many workers and employers both having perfect information about each other and there are no transaction costs. The competitive assumption leads to clear conclusions — workers earn their marginal product of labour.

Other economists focus on deviations from perfectly competitive labour markets. These include job search, training and gaining-of-experience costs to switch between job types, efficiency wage models and oligopsony / monopsonistic competition.

Neoclassical microeconomic model — Supply

Households are suppliers of labour. In microeconomics theory, people are assumed rational and seeking to maximize their utility function. In this labour market model, their utility function is determined by the choice between income and leisure. However, they are constrained by the waking hours available to them.

Let w denote hourly wage. Let k denote total waking hours. Let L denote working hours. Let π denote other incomes or benefits. Let A denote leisure hours.

The utility function and budget constraint can be expressed as following:

max U(w L + π, A) such that L + A ≤ k.

This can be shown in a diagram (below) that illustrates the trade-off between allocating your time between leisure activities and income generating activities. The linear constraint line indicates that there are only 24 hours in a day, and individuals must choose how much of this time to allocate to leisure activities and how much to working. (If multiple days are being considered the maximum number of hours that could be allocated towards leisure or work is about 16 — Everyone has to sleep eventually!) This allocation decision is informed by the curved indifference curve labelled IC. The curve indicates the combinations of leisure and work that will give the individual a specific level of utility. The point where the highest indifference curve is just tangent to the constraint line (point A), illustrates the short-run equilibrium for this supplier of labour services.

The Income/Leisure trade-off in the short run