How much do obstetricians improve from the time they leave medical school to when they have an established practice? "Improvement" meaning fewer complications for mother or child during delivery. It was widely assumed that experience improved obstetricians' work over the first five or so years out of school at which time they hit a "pleateau" of expertise. But a new study of the "experience-performance" relationship among obstetricians in New York and Florida during the period 1992-2009 has found that not to be true. Watch the surprising findings.