From Martin Wolf's column in today's Financial Times:
"In a heroic paper, Bradford De Long of the University of California at Berkeley has estimated the population, total income and real income per head of humanity over the past million years.*
A thousand years ago, he says, the world's population was some 270m; in 1700, at the dawn of the industrial revolution, it was 600m; today it is 6.3bn. A thousand years ago, world gross product (in dollars with a constant 1990 purchasing power) was $35bn; by 1700, it was $100bn; today it is $41,000bn. And a thousand years ago, average world real income per head was $130; by 1700, it was $160; today, it is $6,500."
De Long's paper is at <http://econ161.berkeley.edu/TCEH/1998_Draft/World_GDP/Estimating_Worl d_GDP.html>.
Doug