"In our recent research, we document that mirroring the general rise in income inequality (documented by Piketty and his collaborators, among many others), there has been a similar concentration in individual campaign contributions. Figure 2 shows that the share of campaign contributions coming from the richest ten percent of Census tracts went from about 40% of the total in 1980 to almost 55% in 2020. Meanwhile, the share of the bottom fifty percent of tracts halved, from almost 30% to less than 15%."