For decades, workers migrated to big cities in America that promised abundant jobs and decent wages — in clerical offices in New York, at shipbuilding yards in Oakland, on auto assembly lines around Detroit.

Big, dense cities offered not just better pay for lower-skilled workers; cities offered them better kinds of jobs.

This is much less true today, as workers hurt by the decline in manufacturing know. Because of this, cities no longer offer low-skilled workers the economic advantages they once did, according to new analysis by the M.I.T. economist David Autor.

Workers, whether with a college degree or not, could long count on earning more in denser urban areas than in rural ones. Today, that pattern holds for highly educated workers — and has in fact grown much stronger. For workers without any college education, the added wage benefits of dense cities have mostly disappeared in Mr. Autor’s data: