An important stylized fact about labor markets is that workers with longer seniority with their current employer have higher earnings than other workers with the same total labor market experience. This study shows that the measured positive cross-sectional return to seniority is largely a statistical artifact due to the correlation of seniority with an omitted variable representing the quality of the worker, job, or worker-employer match. The implication is that earnings do not, in fact, rise very much with seniority.