The seminal work of Okun (1962) presented the inverse relationship between changes in unemployment and the growth rate of real GNP. Thereafter the deviation of unemployment from the natural rate of unemployment and the deviation of real output from potential output is known as Okun’s law. This law can be presented as follows:
U −UN = − 1/2 (Y −Y p )
where U is the unemployment rate, and UN represents the natural rate of unemployment. Y is the real output in logs and Yp is potential output in logs. According to the equation above , each one percentage point increase in real output leads to a one-half percentage point decrease in the unemployment rate. Broadly speaking, real output greater than its potential output leads to decline in unemployment rate.