Whether you embrace risk when you invest or do all you can to avoid it, your behavior appears to be driven more by your genes than your age, gender, education or wealth.

That’s the surprising conclusion of a recent study, “Nature or Nurture: What Determines Investor Behavior?” by Amir Barnea and Henrik Cronqvist of Claremont McKenna College and Stephan Siegel of the University of Washington. The trio studied personal financial data collected by the Swedish government, comparing it with information on nearly 38,000 twins in the Swedish Twin Registry. They examined each twin’s participation in the stock market, their allocation of assets and the risk levels of their portfolios.

The results? Identical twins, who share all their genetic material, are much more likely to invest similarly than non-identical twins, who share an average of 50% of their genetic material. Moreover, the investment similarities between random members of the population were even lower. For instance, when looking at participation in the stock market, the researchers found that identical twins acted the same — that is, either both had invested in equities, or both had not — about 30% of the time. That compares with a correlation of about 15% for non-identical twins. The correlation between random investors was negligible.

The results were similar when the researchers examined the proportion of each twins’ portfolios that were allocated to equities. “An individual’s genetic composition is an important determinant of the individual’s investment behavior,” the researchers write.

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Does this mean that financial education has no value, and that your portfolio's up and downs were determined before you even knew what the Dow Jones Industrial Average meant? Not at all, says Siegel of the University of Washington. To be sure, genetic makeup appears to account for 30% to 40% of investor behavior. However, that still leaves 60% to 70% that reflects individual choices and behavior. “It’s not that genes determine everything,” he says. “There’s still a lot of possibility (for investors) to control their outcomes.”

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