Fast economic growth tends to reduce the unemployment rate. So how low can the unemployment rate go? You might be tempted to say zero, but that isn’t feasible. Over the past half-century, the national unemployment rate has never dropped below 2.9%.

How can there be so much unemployment even when many businesses are having a hard time finding workers? To answer this question, we need to examine the nature of labor markets and why they normally lead to substantial measured unemployment even when jobs are plentiful. Our starting point is the observation that even in the best of times, jobs are constantly being created and destroyed.

Even during good times, most Americans know someone who has lost his or her job. In July 2007, the U.S. unemployment rate was only 4.7%, relatively low by historical standards. Yet in that month there were 4.5 million “job separations”—terminations of employment that occur because a worker is either fired or quits voluntarily.

There are many reasons for such job loss. One is structural change in the economy: industries rise and fall as new technologies emerge and consumers’ tastes change. For example, employment in high-tech industries such as telecommunications surged in the late 1990s but slumped severely after 2000. However, structural change also brings the creation of new jobs: after 2000, the number of jobs in the American health care sector surged as new medical technologies and the aging of the population increased the demand for medical care. Poor management performance or bad luck at individual companies also leads to job loss for their employees. For example, in 2009 General Motors announced plans to eliminate 47,000 jobs after several years of lagging sales, even as Japanese companies such as Toyota were opening new plants in North America to meet growing demand for their cars.

Continual job creation and destruction are a feature of modern economies, making a naturally occurring amount of unemployment inevitable. Within this naturally occurring amount, there are two types of unemployment—frictional and structural.

When a worker loses a job involuntarily due to job destruction, he or she often doesn’t take the first new job offered. For example, suppose a skilled programmer, laid off because her software company’s product line was unsuccessful, sees a help-wanted ad for clerical work online. She might respond to the ad and get the job—but that would be foolish. Instead, she should take the time to look for a job that takes advantage of her skills and pays accordingly. In addition, individual workers are constantly leaving jobs voluntarily, typically for personal reasons—family moves, dissatisfaction, and better job prospects elsewhere.

Economists say that workers who spend time looking for employment are engaged in job search. If all workers and all jobs were alike, job search wouldn’t be necessary; if information about jobs and workers was perfect, job search would be very quick. In practice, however, it’s normal for a worker who loses a job, or a young worker seeking a first job, to spend at least a few weeks searching.

Frictional unemployment is unemployment due to the time workers spend in job search. A certain amount of frictional unemployment is inevitable due to the constant process of economic change. Thus even in 2007, a year of low unemployment, there were 62 million “job separations,” in which workers left or lost their jobs. Total employment grew because these separations were more than offset by more than 63 million hires. Inevitably, some of the workers who left or lost their jobs spent at least some time unemployed, as did some of the workers newly entering the labor force.

Figure 8-7 shows the average monthly flows of workers among three states: employed, unemployed, and not in the labor force during 2007, a year of relatively low unemployment. What the figure suggests is how much churning is constantly taking place in the labor market. An inevitable consequence of that churning is a significant number of workers who haven’t yet found their next job—that is, frictional unemployment.

A limited amount of frictional unemployment is relatively harmless and may even be a good thing. The economy is more productive if workers take the time to find jobs that are well matched to their skills, and workers who are unemployed for a brief period while searching for the right job don’t experience great hardship. In fact, when there is a low unemployment rate, periods of unemployment tend to be quite short, suggesting that much of the unemployment is frictional.

Figure 8-8 shows the composition of unemployment for all of 2007, when the unemployment rate was only 4.6%. Thirty-six percent of the unemployed had been unemployed for less than 5 weeks, and only 33% had been unemployed for 15 or more weeks. Only about one in six unemployed workers were considered to be “long-term unemployed”—unemployed for 27 or more weeks.

In periods of higher unemployment, however, workers tend to be jobless for longer periods of time, suggesting that a smaller share of unemployment is frictional. Figure 8-9 shows the fraction of the unemployed who had been out of work for six months or more from 2007 to mid-2014. It jumped to 45% after the Great Recession, and was still historically high five years after the recession officially ended.

Frictional unemployment exists even when the number of people seeking jobs is equal to the number of jobs being offered—that is, the existence of frictional unemployment doesn’t mean that there is a surplus of labor. Sometimes, however, there is a persistent surplus of job-seekers in a particular labor market, even when the economy is at the peak of the business cycle. There may be more workers with a particular skill than there are jobs available using that skill, or there may be more workers in a particular geographic region than there are jobs available in that region. Structural unemployment is unemployment that results when there are more people seeking jobs in a particular labor market than there are jobs available at the current wage rate.

The supply and demand model tells us that the price of a good, service, or factor of production tends to move toward an equilibrium level that matches the quantity supplied with the quantity demanded. This is equally true, in general, of labor markets.

Figure 8-10 shows a typical market for labor. The labor demand curve indicates that when the price of labor—the wage rate—increases, employers demand less labor. The labor supply curve indicates that when the price of labor increases, more workers are willing to supply labor at the prevailing wage rate. These two forces coincide to lead to an equilibrium wage rate for any given type of labor in a particular location. That equilibrium wage rate is shown as W_E.

Even at the equilibrium wage rate W_E, there will still be some frictional unemployment. That’s because there will always be some workers engaged in job search even when the number of jobs available is equal to the number of workers seeking jobs. But there wouldn’t be any structural unemployment in this labor market. Structural unemployment occurs when the wage rate is, for some reason, persistently above W_E. Several factors can lead to a wage rate in excess of W_E, the most important being minimum wages, labor unions, efficiency wages, the side effects of government policies, and mismatches between employees and employers.

Minimum Wages A minimum wage is a government-mandated floor on the price of labor. In the United States, the national minimum wage in early 2014 was $7.25 an hour. A number of state and local governments also determine the minimum wage within their jurisdictions, typically for the purpose of setting it higher than the federal level. For example, the city of Seattle has set a minimum wage at $15 an hour. For many American workers, the minimum wage is irrelevant; the market equilibrium wage for these workers is well above the national price floor. But for less skilled workers, the minimum wage may be binding—it affects the wages that people are actually paid and can lead to structural unemployment in particular markets for labor. Other wealthy countries have higher minimum wages; for example, in 2014 the French minimum wage was 9.40 euros an hour, or around $12.40. In these countries, the range of workers for whom the minimum wage is binding is larger.

Figure 8-10 shows the effect of a binding minimum wage. In this market, there is a legal floor on wages, W_F, which is above the equilibrium wage rate, W_E. This leads to a persistent surplus in the labor market: the quantity of labor supplied, Q_S, is larger than the quantity demanded, Q_D. In other words, more people want to work than can find jobs at the minimum wage, leading to structural unemployment.

Given that minimum wages—that is, binding minimum wages—generally lead to structural unemployment, you might wonder why governments impose them. The rationale is to help ensure that people who work can earn enough income to afford at least a minimally comfortable lifestyle. However, this may come at a cost, because it may eliminate the opportunity to work for some workers who would have willingly worked for lower wages. As illustrated in Figure 8-10, not only are there more sellers of labor than there are buyers, but there are also fewer people working at a minimum wage (Q_D) than there would have been with no minimum wage at all (Q_E).

Although economists broadly agree that a high minimum wage has the employment-reducing effects shown in Figure 8-10, there is some question about whether this is a good description of how the U.S. minimum wage actually works. The minimum wage in the United States is quite low compared with that in other wealthy countries. For three decades, from the 1970s to the mid-2000s, the American minimum wage was so low that it was not binding for the vast majority of workers.

In addition, some researchers have produced evidence showing that increases in the minimum wage actually lead to higher employment when, as was the case in the United States at one time, the minimum wage is low compared to average wages. They argue that firms that employ low-skilled workers sometimes restrict their hiring in order to keep wages low and that, as a result, the minimum wage can sometimes be increased without any loss of jobs. Most economists, however, agree that a sufficiently high minimum wage does lead to structural unemployment.

Labor Unions The actions of labor unions can have effects similar to those of minimum wages, leading to structural unemployment. By bargaining collectively for all of a firm’s workers, unions can often win higher wages from employers than workers would have obtained by bargaining individually. This process, known as collective bargaining, is intended to tip the scales of bargaining power more toward workers and away from employers. Labor unions exercise bargaining power by threatening firms with a labor strike, a collective refusal to work. The threat of a strike can have serious consequences for firms. In such cases, workers acting collectively can exercise more power than they could if acting individually.

Employers have acted to counter the bargaining power of unions by threatening and enforcing lockouts—periods in which union workers are locked out and rendered unemployed—while hiring replacement workers.

When workers have increased bargaining power, they tend to demand and receive higher wages. Unions also bargain over benefits, such as health care and pensions, which we can think of as additional wages. Indeed, economists who study the effects of unions on wages find that unionized workers earn higher wages and more generous benefits than non-union workers with similar skills. The result of these increased wages can be the same as the result of a minimum wage: labor unions push the wage that workers receive above the equilibrium wage. Consequently, there are more people willing to work at the wage being paid than there are jobs available. Like a binding minimum wage, this leads to structural unemployment. In the United States, however, due to a low level of unionization, the amount of unemployment generated by union demands is likely to be very small.

Efficiency Wage Actions by firms can contribute to structural unemployment. Firms may choose to pay efficiency wages—wages that employers set above the equilibrium wage rate as an incentive for their workers to perform better.

Employers may feel the need for such incentives for several reasons. For example, employers often have difficulty observing directly how hard an employee works. They can, however, elicit more work effort by paying above-market wages: employees receiving these higher wages are more likely to work harder to ensure that they aren’t fired, which would cause them to lose their higher wages.

When many firms pay efficiency wages, the result is a pool of workers who want jobs but can’t find them. So the use of efficiency wages by firms leads to structural unemployment.

Side Effects of Government Policies In addition, government policies designed to help workers who lose their jobs can lead to structural unemployment as an unintended side effect. Most economically advanced countries provide benefits to laid-off workers as a way to tide them over until they find a new job. In the United States, these benefits typically replace only a small fraction of a worker’s income and expire after 26 weeks. (This was extended in some cases to 99 weeks during the period of high unemployment in 2009–2011). In other countries, particularly in Europe, benefits are more generous and last longer. The drawback to this generosity is that it reduces a worker’s incentive to quickly find a new job. During the 1980s, it was often argued that unemployment benefits in some European countries were one of the causes of Eurosclerosis, persistently high unemployment that afflicts a number of European economies.

Mismatches Between Employees and Employers It takes time for workers and firms to adjust to shifts in the economy. The result can be a mismatch between what employees have to offer and what employers are looking for. A skills mismatch is one form; for example, in the aftermath of the housing bust of 2009, there were more construction workers looking for jobs than were available. Another form is geographic as in Michigan, which has had a long-standing surplus of workers after its auto industry declined. Until the mismatch is resolved through a big enough fall in wages of the surplus workers that induces retraining or relocation, there will be structural unemployment.

Because some frictional unemployment is inevitable and because many economies also suffer from structural unemployment, a certain amount of unemployment is normal, or “natural.” Actual unemployment fluctuates around this normal level. The natural rate of unemployment is the normal unemployment rate around which the actual unemployment rate fluctuates. It is the rate of unemployment that arises from the effects of frictional plus structural unemployment. Cyclical unemployment is the deviation of the actual rate of unemployment from the natural rate; that is, it is the difference between the actual and natural rates of unemployment. As the name suggests, cyclical unemployment is the share of unemployment that arises from the downturns of the business cycle.

We’ll see in Chapter 16 that an economy’s natural rate of unemployment is a critical policy variable because a government cannot keep the unemployment rate persistently below the natural rate without leading to accelerating inflation.

We can summarize the relationships between the various types of unemployment as follows:

Perhaps because of its name, people often imagine that the natural rate of unemployment is a constant that doesn’t change over time and can’t be affected by government policy. Neither proposition is true. Let’s take a moment to stress two facts: the natural rate of unemployment changes over time, and it can be affected by government policies.

Private-sector economists and government agencies need estimates of the natural rate of unemployment both to make forecasts and to conduct policy analyses. Almost all these estimates show that the U.S. natural rate rises and falls over time. For example, the Congressional Budget Office, the independent agency that conducts budget and economic analyses for Congress, believes that the U.S. natural rate of unemployment was 5.3% in 1950, rose to 6.3% by the end of the 1970s, but has fallen to 5.2% at the end of 2014. European countries have experienced even larger swings in their natural rates of unemployment.

What causes the natural rate of unemployment to change? The most important factors are changes in labor force characteristics, changes in labor market institutions, and changes in government policies. Let’s look briefly at each factor.

Changes in Labor Force Characteristics In 2007 the rate of unemployment in the United States was 4.6%. Young workers, however, had much higher unemployment rates: 15.7% for teenagers and 8.2% for workers aged 20 to 24. Workers aged 25 to 54 had an unemployment rate of only 3.7%.

In general, unemployment rates tend to be lower for experienced than for inexperienced workers. Because experienced workers tend to stay in a given job longer than do inexperienced ones, they have lower frictional unemployment. Also, because older workers are more likely than young workers to be family breadwinners, they have a stronger incentive to find and keep jobs.

One reason the natural rate of unemployment rose during the 1970s was a large rise in the number of new workers—children of the post–World War II baby boom entered the labor force, as did a rising percentage of married women. As Figure 8-11 shows, both the percentage of the labor force less than 25 years old and the percentage of women in the labor force grew rapidly in the 1970s. By the end of the 1990s, however, the share of women in the labor force had leveled off and the percentage of workers under 25 had fallen sharply. As a result, the labor force as a whole is more experienced today than it was in the 1970s, one likely reason that the natural rate of unemployment is lower today than in the 1970s.

Changes in Labor Market Institutions As we pointed out earlier, unions that negotiate wages above the equilibrium level can be a source of structural unemployment. Some economists believe that the high natural rate of unemployment in Europe, discussed in the Global Comparison, is caused, in part, by strong labor unions. In the United States, a sharp fall in union membership after 1980 may have been one reason the natural rate of unemployment fell between the 1970s and the 1990s.

Other institutional changes may also be at work. For example, some labor economists believe that temporary employment agencies, which have proliferated in recent years, have reduced frictional unemployment by helping match workers to jobs. Furthermore, as discussed in the Business Case at the end of the chapter, websites such as Elance-oDesk may have reduced frictional unemployment.

Technological change, coupled with labor market institutions, can also affect the natural rate of unemployment. Technological change tends to increase the demand for skilled workers who are familiar with the relevant technology and reduce the demand for unskilled workers. Economic theory predicts that wages should increase for skilled workers and decrease for unskilled workers as technology advances. But if wages for unskilled workers cannot go down—say, due to a binding minimum wage—increased structural unemployment, and therefore a higher natural rate of unemployment, will result during periods of faster technological change.

Changes in Government Policies A high minimum wage can cause structural unemployment. Generous unemployment benefits can increase both structural and frictional unemployment. So government policies intended to help workers can have the undesirable side effect of raising the natural rate of unemployment.

Some government policies, however, may reduce the natural rate. Two examples are job training and employment subsidies. Job-training programs are supposed to provide unemployed workers with skills that widen the range of jobs they can perform. Employment subsidies are payments either to workers or to employers that provide a financial incentive to accept or offer jobs.