Adding in the cuts to Social Security, Medicaid, education and other programs that Republicans are planning to cull to pay for the tax reductions, the cost to poor and middle-income families would be even greater.

And this presents an immediate ethical problem. Students of the history of economic thought learn early on that taking money from the poor and the middle class to give to the rich tends to reduce overall welfare for the simple reason that an extra dollar provides much more to those who have few of them than to those already rolling in money. Most conventional proposals to increase general welfare support redistributing in the other direction.

Indeed, from Charles I. Jones and Peter J. Klenow at Stanford University to economists at the Organization for Economic Cooperation and Development, most analysts agree that pumping up income growth is not automatically equivalent to increasing welfare. It depends on whose income grows.

There are policies that might trim economic growth and still vastly improve living standards for most Americans. And there are others that might nudge growth ahead and still do more damage than good.

This is particularly important to keep in mind when policies to increase growth are so hard to come by. Jason Furman, who headed President Barack Obama’s Council of Economic Advisers during his second term, notes that this is not limited to taxes. Whether it is changes in regulations or trade agreements, tax cuts or public investment, policy can’t do much to bolster growth in a well-developed economy like that of the United States. It mostly just changes how the economic pie is shared.

“For mature economies with mature institutions, the difference in growth rates that results from different policies is considerably lower than one might suspect,” he wrote. “The growth effects of tax changes are about an order of magnitude smaller than the distributional effects of tax changes.”

According to Mr. Furman’s analysis, changes in tax policy since 1986 — including the Bush tax cuts and increases in taxes in the Clinton and Obama administrations — altogether raised the after-tax income of the bottom 60 percent of Americans by more than 6.5 percent. Meanwhile, they reduced the income of the 1-percenters at the top by more than 12 percent.