By 2018, 59 of the Forbes 400 had made their fortunes in technology, including six of the top ten: Jeff Bezos, No. 1; Bill Gates No. 2; Mark Zuckerberg, No. 4; Larry Ellison, No. 5; Larry Page, number 6; and Sergey Brin number 9. Eighty-eight more made their money in the financial sector. In contrast to the 1982 Forbes list, only 14 on the 2018 list made their money in manufacturing and 24 in energy.

“The 400 have trended steadily to the left,” conclude Bonica and Rosenthal.

The two authors write that from 1989 to 2017, members of the Forbes 400 have fared much better under Democratic presidents than Republican presidents: The 400 “did very well under the two Democrats, Clinton and Obama. They did not do well under either Bush.”

Bonica and Rosenthal’s analysis may prove troubling for those seeking to slow or reverse increasing wealth and income inequality. As the Forbes 400 moves toward the Democratic Party, they write, “Inequality in campaign contributions in the American plutocracy has grown hand in hand with the growth in economic inequality.”

They go on to raise another basic question: Does increased support for Democrats among the affluent and the rich undermine efforts to stem the growth of inequality?

The historic rise in inequality in recent decades has not ushered in an era of Republican fund-raising dominance. On the contrary, Democrats have made substantial gains against Republicans in recent decades while inequality was on the rise.

In a separate essay, published on the Scholars’ Strategy Network, which discusses the implications of their work, Bonica and Rosenthal wrote:

The superrich control resources that parties and politicians require and, as a result, are courted. Politicians have incentives to pay attention to the policy concerns that animate wealthy donors on left and right alike — and this dynamic influences public discussion and policymaking.

The continued concentration of money at the top, they write, translates into more political power:

The ideas, values, and preferences of wealthy donors distort the focus of U.S. democracy more than individuals’ desires to grow their already vast fortunes. Rather than worry about individual corruption, citizens and leaders should worry about the many ways money in politics can amplify the voices of the privileged few over those of the majority. As wealth concentration grows, so will uneven political influence.

Bonica has turned tracking campaign contributions by wealth and occupation into a specialty.

He provided The Times with data extending from 1980 to 2016 covering the contribution patterns of donors who gave the largest amount of money in each election cycle. (Roughly a quarter of Bonica’s list overlaps with the Forbes 400 list.)

In the 1979-80 presidential election cycle, 71 percent of the top 400 donors gave to Republicans and to right-of-center political action committees, while 29 percent gave to Democrats and left-of-center PACS, a 42-point difference. In the 2015-16 presidential cycle, 54 percent gave to Republicans and right-leaning PACs, and 46 percent gave to Democrats, an 8-point difference.