Heh. just another small anecdote.
So if culture were the determinant factor, shouldn't all Iowa farm kids be economically rising? Yet few are; in our neighborhood the rest of our generation are working clerical, farm-services or trades. I guess that's upward too, farmer is pretty much the bottom.
However, the fact that nearly none of my generation took up farming has less to do with social mobility than it does with the changes in the farming landscape. All farms are corporate now; the family farm is largely a myth. It takes $1M+ to get into farming.
Maybe its observer bias; my family is certainly not typical. But who's is?
"I suspect that looking at incomes (or genes) rather misses the root of social mobility or lack of it. I think the more major difference is simply cultural."
Maybe you should give credit where credit is due? Perhaps you are being sarcastic but it seems like everyone in your family has noble professions, at least by my standards...