About 30% of workers in the Current Population Survey have earnings imputed. Wage gap estimates are biased toward zero when the attribute being studied (e.g., union status) is not a criterion used to match donors to nonrespondents. An expression for “match bias” is derived in which attenuation equals the sum of match error rates. Attenuation can be approximated by the proportion with imputed earnings. Union wage gap estimates with match bias removed are presented for 1973–2001. Estimates for recent years are biased downward 5 percentage points. Bias in gap estimates accompanying other non–match criteria (public sector, industry, etc.) is examined.

Wages for black and white workers are substantially lower in occupations with a high density of black employees, following standard controls. Such correlations can exist absent discrimination or as a result of discrimination. In wage level equations, partial correlations fall sharply after controlling for occupational skills. Longitudinal estimates accounting for worker heterogeneity indicate little wage change associated with changes in racial composition. Results support a “quality sorting” rather than discrimination explanation, with racial density serving as an index of unmeasured skills. Discrimination reflected in racial wage gaps occurs within occupations or across occupations in a manner uncorrelated with racial composition.