On the other hand, cyclical unemployment, structural unemployment, and classical unemployment are largely involuntary in nature. However, the existence of structural unemployment may reflect choices made by the unemployed in the past, and classical (natural) unemployment may result from the legislative and economic choices made by labour unions or political parties.

The clearest cases of involuntary unemployment are those with fewer job vacancies than unemployed workers even when wages are allowed to adjust and so even if all vacancies were to be filled, some unemployed workers would still remain. That happens with cyclical unemployment, as macroeconomic forces cause microeconomic unemployment, which can boomerang back and exacerbate those macroeconomic forces.

Out of Work: Unemployment and Government in the Twentieth-Century America
US unemployment rate, 1990—2022. The increase in unemployment during recessions (shaded) is called cyclical unemployment.

With cyclical unemployment, the number of unemployed workers exceeds the number of job vacancies and so even if all open jobs were filled, some workers would still remain unemployed. Some associate cyclical unemployment with frictional unemployment because the factors that cause the friction are partially caused by cyclical variables. For example, a surprise decrease in the money supply may suddenly inhibit aggregate demand and thus inhibit labor demand.

Structural unemployment occurs when a labour market is unable to provide jobs for everyone who wants one because there is a mismatch between the skills of the unemployed workers and the skills needed for the available jobs. Structural unemployment is hard to separate empirically from frictional unemployment except that it lasts longer. As with frictional unemployment, simple demand-side stimulus will not work to abolish this type of unemployment easily.

Seasonal unemployment may be seen as a kind of structural unemployment since it is linked to certain kinds of jobs (construction and migratory farm work). The most-cited official unemployment measures erase this kind of unemployment from the statistics using "seasonal adjustment" techniques. That results in substantial and permanent structural unemployment.

Workers and employers accept a certain level of imperfection, risk or compromise, but usually not right away. They will invest some time and effort to find a better match. That is, in fact, beneficial to the economy since it results in a better allocation of resources. However, if the search takes too long and mismatches are too frequent, the economy suffers since some work will not get done. Therefore, governments will seek ways to reduce unnecessary frictional unemployment by multiple means including providing education, advice, training, and assistance such as daycare centers.

The statistic also does not count the "underemployed", those working fewer hours than they would prefer or in a job that fails to make good use of their capabilities. In addition, those who are of working age but are currently in full-time education are usually not considered unemployed in government statistics. Traditional unemployed native societies who survive by gathering, hunting, herding, and farming in wilderness areas may or may not be counted in unemployment statistics.

Though many people care about the number of unemployed individuals, economists typically focus on the unemployment rate, which corrects for the normal increase in the number of people employed caused by increases in population and increases in the labour force relative to the population. The unemployment rate is expressed as a percentage and calculated as follows:

According to the OECD, Eurostat, and the US Bureau of Labor Statistics the unemployment rate is the number of unemployed people as a percentage of the labour force.

"An unemployed person is defined by Eurostat, according to the guidelines of the International Labour Organization, as:

Note: "Marginally attached workers" are added to the total labour force for unemployment rate calculation for U4, U5, and U6.

The last people are "involuntary part-time" workers, those who are underemployed, such as a computer programmer who is working in a retail store until he can find a permanent job, involuntary stay-at-home mothers who would prefer to work, and graduate and professional school students who are unable to find worthwhile jobs after they graduated with their bachelor's degrees.

In particular, as of 2005, roughly 0.7% of the US population is incarcerated (1.5% of the available working population). Additionally, children, the elderly, and some individuals with disabilities are typically not counted as part of the labour force and so are not included in the unemployment statistics. However, some elderly and many disabled individuals are active in the labour market.

In the United States, there have been four significant stages of women's participation in the labour force: increases in the 20th century and decreases in the 21st century. Male labor force participation decreased from 1953 to 2013. Since October 2013, men have been increasingly joining the labour force.

That implies that other factors may have contributed to women choosing to invest in advancing their careers. One factor may be that an increasing number of men delayed the age of marriage, which allowed women to marry later in life without them worrying about the quality of older men. Other factors include the changing nature of work, with machines replacing physical labor, thus eliminating many traditional male occupations, and the rise of the service sector in which many jobs are gender neutral.

Another factor that may have contributed to the trend was the Equal Pay Act of 1963, which aimed at abolishing wage disparity based on sex. Such legislation diminished sexual discrimination and encouraged more women to enter the labor market by receiving fair remuneration to help raising families and children.

The labor force participation rate can decrease when the rate of growth of the population outweighs that of the employed and the unemployed together. The labor force participation rate is a key component in long-term economic growth, almost as important as productivity.

High unemployment can also cause social problems such as crime. If people have less disposable income than before, it is very likely that crime levels within the economy will increase.

The primary benefit of unemployment is that people are available for hire, without being headhunted away from their existing employers. That permits both new and old businesses to take on staff.

Increases in the demand for labour move the economy along the demand curve, increasing wages and employment. The demand for labour in an economy is derived from the demand for goods and services. As such, if the demand for goods and services in the economy increases, the demand for labour will increase, increasing employment and wages.

There are many ways to stimulate demand for goods and services. Increasing wages to the working class (those more likely to spend the increased funds on goods and services, rather than various types of savings or commodity purchases) is one theory that is proposed. Increased wages are believed to be more effective in boosting demand for goods and services than central banking strategies, which put the increased money supply mostly into the hands of wealthy persons and institutions. Monetarists suggest that increasing money supply in general increases short-term demand. As for the long-term demand, the increased demand is negated by inflation. A rise in fiscal expenditures is another strategy for boosting aggregate demand.

Supply-side economics proposes that lower taxes lead to employment growth. Historical state data from the United States shows a heterogeneous result.

According to classical economic theory, markets reach equilibrium where supply equals demand; everyone who wants to sell at the market price can do so. Those who do not want to sell at that price do not; in the labour market, this is classical unemployment. Monetary policy and fiscal policy can both be used to increase short-term growth in the economy, increasing the demand for labour and decreasing unemployment.

There are relatively limited historical records on unemployment because it has not always been acknowledged or measured systematically. Industrialization involves economies of scale, which often prevent individuals from having the capital to create their own jobs to be self-employed. An individual who cannot join an enterprise or create a job is unemployed. As individual farmers, ranchers, spinners, doctors and merchants are organized into large enterprises, those who cannot join or compete become unemployed.

Poverty was a highly visible problem in the eighteenth century, both in cities and in the countryside. In France and Britain by the end of the century, an estimated 10 percent of the people depended on charity or begging for their food.

By 1776, some 1,912 parish and corporation workhouses had been established in England and Wales and housed almost 100,000 paupers.

The scarcity and the high price of labor in the US in the 19th century was well documented by contemporary accounts, as in the following:

Scarcity of labor was a factor in the economics of slavery in the United States.

As new territories were opened and federal land sales were conducted, land had to be cleared and new homesteads established. Hundreds of thousands of immigrants annually came to the US and found jobs digging canals and building railroads. Almost all work during most of the 19th century was done by hand or with horses, mules, or oxen since there was very little mechanization. The workweek during most of the 19th century was 60 hours. Unemployment at times was between one and two percent.

Unemployment in the United Kingdom fell later in the 1930s as the Depression eased, and it remained low (in single figures) after World War II.