The standard explanation of this unhinging, repeated in graduate-school classrooms and in advice to politicians, is technological change. The rise of networked laptops and smartphones and their countless iterations and spawn have helped highly educated professionals create more and more value just as they have created barriers to entry and rendered irrelevant millions of less-educated workers, in places like factory production lines and typing pools. This explanation, known as skill-biased technical change, is so common that economists just call it S.B.T.C. They use it to explain why everyone from the extremely rich to the just-kind-of rich are doing so much better than everyone else.

For two decades, Mishel has been a critic of the S.B.T.C. theory, and that morning in San Diego, he argued that broad technological innovation has been taking place so steadily for so long that the rise of computers simply can’t explain the recent explosion in inequality. After all, when economists talk about technological innovation, they are thinking beyond smartphones; they’re usually considering innovations that affect production. Business innovations — like the railroads, telegraph, Henry Ford’s conveyor belt and the plastic extruders of the 1960s — have occurred for more than a century. Computers and the Internet, Mishel argued, are just new examples on the continuum and cannot explain a development like extreme inequality, which is so recent. So what happened?

The change came around 1978, Mishel said, when politicians from both parties began to think of America as a nation of consumers, not of workers. President Jimmy Carter deregulated the airline, trucking and railroad industries in order to help lower consumer prices. Congress chose to ignore organized labor’s call for laws strengthening union protections. Ever since, Mishel said, each administration and Congress have made choices — expanding trade, deregulating finance and weakening welfare — that helped the rich and hurt everyone else. Inequality didn’t just happen, Mishel argued. The government created it.

After Mishel finished his presentation, David Autor, one of the country’s most celebrated labor economists, took the stage, fumbled for his own PowerPoint presentation and then explained that there was plenty of evidence showing that technological change explained a great deal about the rise of income inequality. Computers, Autor says, are fundamentally different. Conveyor belts and massive steel furnaces made blue-collar workers comparatively wealthier and hurt more highly skilled crafts­people, like blacksmiths and master carpenters, whose talents were disrupted by mass production. The computer revolution, however, displaced millions of workers from clerical and production occupations, forcing them to compete in lower-paying jobs in the retail, fast-food and home health sectors. Meanwhile, computers and the Internet disproportionately helped people like doctors, engineers and bankers in information-intensive jobs. Inequality was merely a side effect of the digital revolution, Autor said; it didn’t begin and end in Washington.

For all their disagreements, Autor and Mishel are allies of sorts. Both are Democrats who have advised President Barack Obama, and both agree that rampant inequality can undermine democracy and economic growth by fostering despair among workers and corruption among the wealthy. This places them in opposition to some right-leaning economists like Gary Becker, a Nobel Prize-winning professor at the University of Chicago, who told me a few years ago that “inequality in earnings has been mainly the good kind,” meaning it rewards those people with the education and skills most needed, helping the economy.