Suppose that we divide the countries of the world into three groups: low income per worker in 1960 (less than 33% of income per worker in the United States), middle income per worker in 1960 (between 33% and 67% of income per worker in the United States), and high income per worker in 1960 (greater than 67% of income per worker in the United States).

(a) Calculate average income per worker for the low income, middle income, and high income countries, respectively, for 1960 and 2007, and calculate the rates of growth of average income for the low, middle, and high income countries between 1960 and 2007.

(b) Do the statistics you calculated in part (a) indicate any tendency for convergence among these three groups of countries?

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