unemployment decreases. Many economists have argued that unemployment increases with increased governmental regulation. For example, minimum wage laws raise the cost of some low-skill laborers above market equilibrium, resulting in increased unemployment as people who wish to work at the going rate cannot (as the new and higher enforced wage is now greater than the value of their labour). Laws restricting layoffs may make businesses less likely to hire in the first place, as hiring becomes more risky. However, that argument overly simplifies the relationship between wage rates and unemployment by ignoring numerous factors that contribute to unemployment. Some, such as Murray Rothbard, suggest that even social taboos can prevent wages from falling to the market-clearing level. In Out of Work: Unemployment and Government in the Twentieth-Century America, economists Richard Vedder and Lowell Gallaway argue that the empirical record of wages rates, productivity, and unemployment in America validates classical unemployment theory. Their data shows a strong correlation between adjusted real wage and unemployment in the United States from 1900 to 1990. However, they maintain that their data does not take into account exogenous events. Cyclical unemployment Cyclical, deficient-demand, or Keynesian unemployment occurs when there is not enough aggregate demand in the economy to provide jobs for everyone who wants to work. Demand for most goods and services falls, less production is needed and consequently, fewer workers are needed, wages are sticky and do not fall to meet the equilibrium level, and unemployment results. Its name is derived from the frequent ups and downs in the business cycle, but unemployment can also be persistent, such as during the Great Depression. 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. Keynesian economists, on the other hand, see the lack of supply of jobs as potentially resolvable by government intervention. One suggested intervention involves deficit spending to boost employment and goods demand. Another intervention involves an expansionary monetary policy to increase the supply of money, which should reduce interest rates, which, in turn, should lead to an increase in non-governmental spending. Unemployment under "full