I updated the industry and occupational rankings graph to include all repeat contributors in election cycles between 1990 and 2008. Anyone who has seen the previous figure will notice an overall shift the right for most industries and occupations. By including two-decades worth of election cycles, the estimates tend to smooth out the shift to the left caused by the unusually favorable climate for Democrats during the 2008 election. On the other hand, it tends to understate the extent to which certain industries have moved to the extremes in recent years.
I also added a few features to the plots in response to being rightly called out for the sloppy/incomplete presentation of the previous graph by an expert on statistical graphics. These new and improved graphs include horizontal bars that represent the 40-60 percentile of each industry/occupation that are intended as rough measures of dispersion–most industries are bimodal, which would make wider distribution bands span nearly the entire graph, hence losing most of their informational content. In addition, the y-axis now indicates the amount given by repeat contributors within each industry/occupation. These amounts would be much larger if non-repeat contributors were included in the sample as well.
Obviously, not all industry and occupational categories could be included in the graphs. I plan to post a spreadsheet with a complete ranking of categories sometime in the near future.