For example, the food stamp program was introduced gradually in the United States from 1961 to 1975. Hilary Hoynes of the University of California, Berkeley, Diane Whitmore Schanzenbach of Northwestern University and Douglas Almond of Columbia University have found that low-income children who benefited from the program were healthier and more likely to be working decades later than otherwise similar children in counties where the program arrived later. There is similar evidence of long-term economic benefits from high-quality childhood education.

What is behind the surge of research in this vein? “It is a combination of data and time,” Ms. Hoynes said. “What we’ve seen so far is just the tip of the iceberg in terms of what is possible.”

The advent of more advanced computer processing power has enabled social scientists to mine administrative data — actual records on individuals — instead of relying on often spotty, inconsistent surveys.

But also important is that a variety of social welfare programs introduced and expanded since the 1960s have now been around long enough, often with periodic changes to their structure, to allow for an analysis of their long-term effects.

Some studies are truly long-term. Anna Aizer of Brown University and three colleagues studied what happened to boys whose families were beneficiaries of the “Mothers’ Pension” program, which from 1911 to 1935 paid cash benefits to poor families in which the breadwinner had died or become disabled. Compared with children in similar circumstances who did not benefit from the program, their incomes were 14 percent higher during their prime working years of 20 to 45. (They also lived longer, got more education and, among those who served in the military in World War II, were taller.)

None of this means that all social welfare programs result in more people working. Receiving unemployment insurance, for example, appears to make people slower to find new work, and the Congressional Budget Office projects that the Affordable Care Act will lead to fewer adults working because they can more easily obtain health care without having an employer.

It also isn’t an assertion that these programs pay for themselves by generating more economic growth. Something like food stamps or the E.I.T.C. can have pro-growth effects while still being costly to the government.