Over the period from B.C. 10,000 to A.D. 1, the world population is estimated to have increased from 4 million to 170 million, while the level of income per capita was constant over time. Assuming that the quantities of human and physical capital per worker did not change, and that the exponent on land in the production function is one-third, calculate the growth rate in productivity over this period. What was the annual growth rate of productivity, A?