1940 Census Records and the Return from Farming

I was lucky that ancestry.com chose NY as one of the first states for which to process 1940 census images, so I was able to see the entries for my family (not me, I just missed it so I'll have to wait another 10 years to see myself recorded).  I had a couple of surprises:

• first, the census for the first and only time asked where people had lived in 1935. Now I had assumed that my neighborhood was stable and unchanging, but it turned out about half the people on the page with my family had moved in the last 5 years.  
• second, my father listed his income as $0.  (Yes, the census bureau was asking about family income back then--our forebears weren't as touchy about releasing personal data as we seem to be today.  Or maybe they had more respect for authority and the establishment.)  Dad was one of the early farmers who participated in a cost-accounting study from Cornell extension.  Not that he was a great record keeper; I'm sure I inherited my disorderly gene from him.  But yearly I think it was he would put on a push to update his cost accounts on the forms Cornell provided him.  I don't remember whether the Extension professor picked them up in person, or dad mailed them off. So I suspect dad's report of $0 was based on his cost accounts, which would have subtracted from his gross income the interest earned on the capital invested.   That used to be a sore point with my mother, who got very fierce about underpaid farmers, often claiming farmers would be better off selling out and investing the returns for a safe return.  The bottom line was the family had a small positive cash flow, but we weren't doing well.