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How to Alleviate Correlation Neglect in Investment Decisions

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Abstract

We experimentally study how presentation formats for return distributions affect investors’ diversification choices. We find that sampling returns alleviates correlation neglect and constitutes an effective way to improve financial decisions. When participants get a description of the probabilities for outcomes of the joint return distribution, we confirm the findings of others that investors neglect the correlation between assets in their diversification choices. However, when participants sample from the joint distribution, they change their allocation between two assets in response to a change in their correlation in the predicted direction. The results are robust across two experiments that have participants with varying experience (students versus private investors). This paper was accepted by Manel Baucells, behavioral economics and decision analysis.

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... When combining information from multiple sources (e.g., for financial forecasts: Budescu and Yu, 2007;Enke and Zimmermann, 2017;Hossain and Okui, 2021;Maines, 1996Maines, , 1990or constructing portfolios of correlated assets: Eyster and Weizsacker, 2016;Laudenbach et al., 2022), most participants exhibit "correlation neglect" (i.e., partially or fully failing to account for correlations), which often leads to reduced decision accuracy. Positive correlations have also been proposed to lead to overconfidence, which has been attributed to failing to account for redundancy (Eyster and Rabin, 2010;Glaeser and Sunstein, 2009;Ortoleva and Snowberg, 2015) or to the false assumption that consistency among information sources suggests higher reliability (Kahneman and Tversky, 1973). ...
... /2024 even in simplified cases, decisions in descriptive scenarios likely rely on very different cognitive mechanisms than decisions that, like ours, are based directly on relatively low-level sensory stimuli. For example, decisions under risk can vary substantially when based on description versus direct experience (Hertwig and Erev, 2009), and giving passive exposure to samples from distributions underlying two correlated assets has been shown to alleviate correlation neglect in subsequent allocation decisions (Laudenbach et al., 2022). ...
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