It's good that you have the S&P as a benchmark. It shows that the median performance of a senator (4%-6%) is lower than expected (10%). Can you add the S&P to the histogram so it's always there? That would make the difference more obvious.
If I return 2% per year, but do so at 1% volatility and zero market exposure, then I can be a highly successful hedge fund after applying 10x leverage.
[1] https://mba.tuck.dartmouth.edu/pages/faculty/ken.french/data...