First and foremost, it should be understood that Okun's Law is an empirical observation. The law is founded in a perceived relationship between gdp and unemployment. In this sense, Okun's Law is an approximation and not rightly a Law derived from theory.
There is some debate as to how much of a decrease in gdp actually occurs from an increase in unemployment, but two leading figures have offered estimations. Martin Prachowny gives the ratio 3:1, such that for every 1% increase in unemployment, a country's gdp drops by 3%. Ben Bernake more recently has offered a revised estimation, placing it closer to 2:1.
Therefore, to find the inverse, a country's GDP would have to grow by 2-3% in order to reduce unemployment by 1%.
