The relationship between an economy's unemployment rate and its gross national product (GNP). Twentieth-century economist Arthur Okun developed this idea, which states that when unemployment falls by 1%, GNP rises by 3%. However, the law only holds true for the U.S. economy, and only applies when the unemployment rate falls between 3-7.5%. Other version of Okun's Law focus on a relationship between unemployment and GDP, whereby a percentage increase in unemployment causes a 2% fall in GDP.