The education reform movement includes efforts to raise teacher quality through stricter certification and licensing provisions. Most US states now require public school teachers to pass a standardized test such as the Praxis. Although any barrier to entry is likely to raise wages in the...

Two ubiquitous empirical regularities in pay distributions are that the variance of wages increases with experience, and innovations in wage residuals have a large, unpredictable component. The leading explanations for these patterns are that over time, either firms learn about worker...