Here is a cross-tabulation of the "yea" vote on the 2014 farm bill and the four Census bureau regions: Northeast (0), South (1), Midwest (2), and West (3).
Fewer than half the legislators in the Northeast voted in favor of the bill. This might have something to do with the cuts to SNAP and increase in crop insurance spending (which offset cuts in direct payments), but I can't be sure. Over 75% of Midwestern legislators voted in favor of the final bill. A majority of Southern and Western legislators voted for the bill but their margins were thinner at 67.5% and 59%.
The correlation between "yea" votes, the percentage of households in a district or state that received SNAP funds in 2011-2013, the farm share of gross state product in 2013, and the percentage of the households in a district or state designated "rural" can give us a basic idea of how these legislative incentives affected the passage of the bill.
There's a weak positive correlation between SNAP household percentage and "yea" votes (0.0036), but it's not statistically significant. Legislators representing states or districts with larger farm economies or rural household percentages were more likely to vote in favor of the bill with correlations of 0.1627 and 0.3267, respectively.
Finally, looking at the correlation between ideology and PAC spending tells an intuitive story: more agricultural PAC money goes to more right-leaning candidates while more environmental PAC money goes to more left-leaning candidates. The correlations of interest are 0.2167 for agricultural PACs and -0.3314 for environmental PACs. Both are statistically significant at the 1% level.
To clarify, the ideology variable ranges from 0 to 1 with extreme left-wing being closer to 0 and extreme right-wing being closer to 1. This doesn't by itself imply that PAC spending by either group buys votes, but it is interesting to see just how strong (or weak, depending on your expectations) these correlations are.
The correlation between environmental PAC spending and ideology is higher because environmental PAC spending seems to be more targeted. While agricultural PACs give quite a bit of money to almost all legislators, environmental PAC spending is lower with relatively high percentages of their total spending going to specific legislators. I'll get into this more later when I have a full summary of the paper. For now I plan to keep sharing interesting information as I go.