Number of Tractors: 1920 US Versus 2000 Africa

The World Bank has a post on agriculture in sub-Saharan Africa.  Now I'm going by memory, which is that Prof. Pollan in Omnivore's Dilemma wrote that the US had 254 tractors on farms in 1920.  I doubted that, and found the Census report 254,000 tractors (Pollan had missed the unit of measure in the table).  So that figure sticks in my mind, although given my advancing age it should be taken with a grain of salt. 

But that's the context in which I read this:

In Sub-Saharan Africa, the trend has been rather different. In 1961, the number of tractors in use was more than in both Asia and the Near East (at 172 000).  After that the number increased slowly to peak at 275 000 by 1990 before declining to 221 000 by 2000.

 In other words, sub-Africa had fewer tractors in 2000 than the US had in 1920.  Further, the population of Africa was about 600 million, while the population of the US was about 100 million.