Does cognitive ability generate superior investment returns independent of risk?
Core argument: Cognitive ability’s capital income gradient is 3x steeper than labor income gradient in log specifications, driven by higher saving rates.
We document three results. First, cognitive ability predicts capital income. Figure 2 plots mean log income and mean income rank against the nine cognitive ability scores reporting test performance on a 1–9 scale, with both series normalized to zero at the lowest score. In the log specification (Panel a), the capital income gradient is roughly three times steeper than the labor income gradient. In the rank specification (Panel b), the ordering reverses: the labor income gradient is steeper, because the heavy right tail of capital income compresses rank differences. Figure 3 provides a complementary perspective, plotting average cognitive ability across percentiles of the labor and capital income distributions. [The relationship between ability and rank flattens at the top of the labor distribution but strengthens at the top of the capital distribution.] Second, the capital-income gradient is only partially explained by labor income: a decomposition shows that ability is associated with higher saving rates and investment returns through channels beyond labor income. Third, the investment return channel is consistent with skill rather than risk compensation, as high-ability individuals earn higher risk-adjusted excess returns while holding portfolios with lower systematic risk.

