People can’t accurately translate a lump sum into monthly income, the study says, and when presented with a lump-sum number of accumulated retirement savings (such as $1,000,000)—as retirement plan statements customarily do—they cannot judge whether that’s enough to support them or not.

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But they err on the side of believing that it is—the “illusion of wealth”—even though whatever lump-sum number the statement may present might be wholly inadequate.

In addition, they may be so under the wealth illusion that they take no action to boost savings and even spend profligately in retirement, believing they have more than they actually do.

In contrast, if they are given a statement that translates that lump sum into an equivalent monthly income at retirement, they react with an “illusion of poverty” and may not believe that it’s enough to get by on. They are more likely to increase their savings level and once retired may hold back on savings more than they need to, believing that they’re in imminent danger of exhausting their money.

In fact, the study cites a related one that “presented 17,000 employees with projected effects of increasing savings rates, expressed in terms of either total accumulation at retirement or total accumulation at retirement in addition to monthly income projections. They found that the addition of projected monthly incomes increased employees’ saving rates more than those who received only projected total accumulations.”

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The “illusion of wealth” study examined “whether people are more or less sensitive to changes in wealth presented as lump sums (e.g., $100,000) or equivalent monthly amounts (e.g., $500 per month for life from age 68).”

Study respondents “were asked to imagine that for each listed amount of money, they had that amount—and only that amount—of money to spend during retirement,” the study says; respondents were also asked to assume they had no assets—house, money, anything—that could be spent beyond the amount they were presented with.

Next, they were shown a table with seven monetary amounts and asked to grade each amount on a seven-point scale that ranged from “totally inadequate” to “totally adequate.”

At the three lowest wealth levels, respondents perceived the lump sums as more adequate for retirement than monthly amounts, while at the three highest wealth levels, they perceived monthly amounts as more adequate than lump sums.

Even when the amounts were roughly equivalent—say, $1,000,000 compared with $5,000 per month of income, the latter of which is approximately what an annuity payment would provide on a million dollars—people perceived the former as “wealth” and the latter as “poverty.”

The study’s authors suggest that reframing retirement savings totals in terms of monthly income during retirement—and presenting that depiction first—would be more helpful in stimulating higher savings rates than just presenting savers with a lump-sum total, which is not only the way most statements provide the information but most online tools do as well.

“[S]aving intentions are more sensitive to wealth expressed as monthly amounts,” the study finds, “rather than lump sums.”