Okun's law refers to the relationship between increases in unemployment and decreases in a country's gross domestic product (GDP). It states that for every 1% increase in unemployment above a "natural" level, that GDP will decrease by anywhere from 2% to 4% from its potential. This law is named after Arthur Okun, the economist who, in 1962, was the first to make detailed observations about this relationship. So-called "natural unemployment" refers to the fact that there will always be at least a certain amount of unemployment in a free market economy, because of voluntary changes in employment and other reasons not related to economic hardship.