The argument between the sides is similar to the classic debate between the hardworking ants and lazy grasshoppers of Aesop’s fable. The financial planning industry says saving, even too much, provides a safety net and peace of mind, and possibly a gift to heirs at the end.

The economists answer that people would get more out of their money by using it when they are younger. “There is risk in saving too much,” Mr. Kotlikoff said. “You could end up squandering your youth rather than your money.”

Mr. Scholz said he and his co-authors of a study, “Are Americans Saving ‘Optimally’ for Retirement?” found oversaving across all economic and education levels and most ethnic or racial groups as well. (It found that Hispanics tended to save less.) Those who were not saving enough were usually missing their target by only a small amount.

The one exception to this optimism involves people who enter retirement single, either because their spouse died early, they divorced, or they never married. The studies found this group did not save enough.

“If they are worried about end-of-life medical expenses or they don’t mind leaving money to their heirs,” Mr. Scholz said, “then oversaving is fine.” The dispute revolves around how financial planners determine how much a person should save. That amount will vary depending on age, income and assets. To simplify the calculations, computer programs resort to rules of thumb.

The starting point for most retirement plans is the so-called replacement rate. It says an American needs an annual income in retirement equal to 75 percent to 86 percent of what he or she earned in the final year of employment. Someone making $100,000 would typically plan for about $85,000 a year in retirement.

Coupling that with a second industry rule of thumb that says retirees should spend no more than about 4 percent of their assets each year to make them last, a typical couple with that level of income should enter retirement with at least $2.1 million in assets, including 401(k)s, I.R.A.’s, stocks and bonds, real estate, cash value life insurance, pensions and Social Security benefits.