On the campaign trail, Hillary Clinton has eloquently defined workers’ rights as human rights. She could assert both more forcefully by championing a stronger federal minimum wage of $15 an hour.

So far, Mrs. Clinton has proposed lifting the federal hourly minimum to $12, from its current level of $7.25 an hour. Bernie Sanders is pushing for $15. Under both proposals, the increase would be phased in over five years, which means 2022 at the earliest, assuming that legislation to raise the minimum becomes law in 2017, the first year of the next president’s term.

Reasonable people can disagree about the ideal level for the minimum wage. There is no doubt, however, that the longer it takes to get to a new minimum, the higher it should be, and that by any political or practical calculation, 2022 is a long way off. This alone argues for Mr. Sanders’s more generous proposal.

Mrs. Clinton has argued that $15 might be too high for employers in low-wage states, causing them to lay off workers or make fewer hires. There is no proof for or against that position. There is solid empirical evidence showing that moderate increases in the minimum wage do not harm employment. But there is no similarly rigorous research on the effects of large increases, mainly because there haven’t been very many, either in the United States or internationally.