When the Dow Jones Industrial Average hit 18,000 a few years back, the nicely rounded number dominated the news. When teens take the SAT, those who just miss scoring a round number are more likely to seek a do-over. And, research shows, major league baseball players are four times more likely to end their seasons with a .300 batting average than a .299.

There's something irresistible about figures ending in zero. But does that extend to our decision-making? Does our instinctive love for round numbers affect our financial plans?

The answer is yes, says Rice Business professor Ajay Kalra. Along with Xiao Liu of NYU Stern and Wei Zhang of Iowa State University, Kalra looked at data from thousands of investors in Target Retirement Funds (TRFs), which generally assume retirement at age 65 and ask employees to pick a fund with a year ending either in zero or five (e.g., 2040, 2045) that is nearest to their planned retirement date.

Investors whose birth year doesn't already end in zero or five must round up or round down to choose their TRF.

The zeros clearly win investors' hearts. Succumbing to what the researchers call "zero bias," investors consistently choose to sink their retirement dollars into funds that end in zero, not five. For many of the investors Kalra and his team looked at, especially older people, men and those with higher incomes, this meant choosing a retirement age of 60 or 70 rather than the standard 65.

The choice was often costly. Many investors who rounded up or down to find a fund year ending in zero exposed themselves to real financial risk.

That's because TRFs are graded portfolios — meaning they start out stock-heavy, move to a mix of stocks and bonds and finally emphasize bonds. Investors who rounded down for a too-young retirement target gave themselves less time to benefit from a stock-dominant portfolio. Investors who rounded up for a too-old retirement target ending in zero contributed less money to their retirement because they assumed they had more time to invest. Investors who rounded down did worse than those who rounded up.

Who is most susceptible to losing hard-earned retirement dollars this way? The researchers looked at people born from the 1950s through the 1980s. Of these investors, those born in years ending between three and seven selected the appropriate fund. The zero bias was prevalent in those born in years ending in eight or nine, who tended to project their retirement age as 60, and those born in years that ended in zero, one or two, who favored retiring at 70.

Overall, the researchers discovered, 34 percent of people born in years ending in eight or nine picked retirement funds that targeted too-early retirement — and ended up financially worse off. Meanwhile, 29 percent of investors born in years ending in the numbers zero, one or two picked later TRFs. With the exception of those who were risk averse, these investors ended up better off than those who chose too-early TRFs. Overall, however, investors who picked funds with mismatched retirement dates (that is, inconsistent with retirement at 65), saw more losses than gains.

The infatuation with zero held up even when the researchers replicated their study in an experimental setting. So they tried something different: they presented participants with math problems to coax a "calculative mindset." It worked. Rather than gravitating to zeros, these investors chose retirement funds that matched their ages. Straight talk in the form of a 30-minute one-on-one financial planning session helped too. At least some investors who got this counseling made better choices.

Rounding up or down to zero can be a nice mental shortcut when stakes are low and time is short. There are good reasons, for example, to go for the zero in calculating sales tax when you're buying a book, or tallying how many party guests want cake.

But when it comes to life savings, instinct-based math can be trouble. Financial firms should be aware of this and discourage preference for the shiny number zero. Advisors should nudge clients toward funds that will truly enhance earnings. Most important, however, investors themselves need to keep their heads, think of the future and resist the allure of round numbers.

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This story originally ran on Rice Business Wisdom. It's based on research by Ajay Kalra, a professor of marketing at Jones Graduate School of Business at Rice University.