The Returns to Education: A Comment

Clark and Nielsen (2026) assemble a large dataset of quasi-experimental studies and argue that the causal return to an extra year of schooling is close to zero once one corrects for the selective publication of statistically significant findings. If correct, this would overturn a central pillar of human capital theory and weaken the empirical case for investing in education. This comment re-examines their own data with the standard battery of publication-bias corrections, including methods that guard against spuriously precise estimates and against p-hacking. Every method points to a return of around 5–6% per additional year of schooling—positive, statistically significant, and far from zero—and the estimate stays well above zero even under the most conservative variants. Clark and Nielsen’s near-zero figure comes instead from a bespoke procedure that assumes large numbers of negative-return studies were suppressed; the distribution of published estimates does not support that assumption, and the same procedure understates even a genuine, positive return in simulation. Publication bias in this literature is real but modest: corrected for properly, the evidence is inconsistent with a near-zero causal return.