Thanks, James and Elisabeth!
James - I came across that website in my searching yesterday, but I think I'm too stupid to read it. So I ignored it.
Elisabeth - That was my guess. I know that now soybean is mostly used for oil and feed for farm animals. Only a small portion goes into food and a very small portion for the foods we think of with soybeans - vegetarian things like tofu (most of the rest of the food is fillers like you said was happening in the 80s - I think I read somewhere that McDonald's hamburgers are mostly soybeans).
Sara sent me a link that lists all the subsidies in sent to Kansas in total for 1995-2006 and it has soybeans as #6. So lower down than I thought (at least for Kansas), but clearly it was used before tofu started popping up everywhere or it wouldn't make it onto the table (which only list the top 10 subsidies for the 11 year period).
