I heard from 'This American Life' host Ira Glass that the US government stopped keeping statistics on number of people living on farms in 1993. He said that the number was so small (less than 1 percent) that it didn't really make sense to keep track of it anymore.
However, the USDA Economics, Statistics and Market Information System (ESMIS), a collaboration between Cornell University and of the U.S. Department of Agriculture, has been keeping track. They offers us a lot of paperwork with a lot of numbers buried in confusing text and all in a completely unusable format. It is precisely what Hans Rosling is always on about.
Anyone who cares to take the time to find some statistics on farming demographics in the US can look to ESMIS to find the data. I've just taken a little time to look through the statistics and see what they have to say about the number of farms and farm area. It turns out that the total number of farms has been pretty steady since a big jump back in 2007. According to the statistics the US went from 2,088,790 farms to 2,204,950 that year.
That same 2007 jump in the number of farms also corresponds to a big drop (yes drop) in the average farm size.
Props to the Greenhorns and the Young Organics and the Slow Food movers and shakers. They are really doing it.