Calculate the standard deviation of income per worker for the countries of the world for 1960 and 2007. Does this indicate that convergence is occurring or not? For the same years, calculate the standard deviation of income per worker for the poor countries (less than 20% of income per worker in the United States in 1960) and for the rich countries (greater than 20% of income per worker in the United States in 1960). What does this tell you about convergence among the rich and the poor?

To answer this question, use the Penn World Table data available at http://datacentre2.chass.utoronto.ca/pwt62/