Maybe gdp is not the best normalizing variable to choose, any suggestions on something better? In the context of the previous 25 years its not. "following Worl

Maybe gdp is not the best normalizing variable to choose, any suggestions on something better? In the context of the previous 25 years its not. "following World War II tax increases, top marginal individual tax rates stayed near or above 90%, and the effective tax rate at 70% for the highest incomes (few paid the top rate), until 1964 when the top marginal tax rate was lowered to 70%..."- wikipedia it would be interesting to have the full historical data set to play with