David Card shared the 2021 economics Nobel for empirical labour-economics work built on natural experiments

The 2021 Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel went to David Card, Joshua Angrist, and Guido Imbens. Card was cited "for his empirical contributions to labour economics"; Angrist and Imbens were recognized "for their methodological contributions to the analysis of causal relationships." The award is the field-level recognition of the "credibility revolution" — the shift toward drawing causal conclusions from natural experiments rather than from theory or structural models alone.

Card's headline results share a shape: a surprising conclusion extracted from a natural experiment. His 1990 Mariel Boatlift study found no wage effect from a large low-skill refugee inflow, and his New Jersey/Pennsylvania minimum-wage study (early 1990s, with Alan Krueger) challenged the conventional wisdom that raising the minimum wage necessarily reduces employment. Both cut against textbook predictions and both rest on comparisons the world happened to run rather than on a model's assumptions.

The methods this program legitimized include the synthetic control estimator later used to re-referee Card's own Mariel result — and the same natural-experiment logic animates the vault's structural-vs-selection framing in a different migration case.