Many theoretical models of labor market search imply a tight link between worker flows (hires and separations) and job gains and losses at the employer level. We use rich establishment-level data to assess several theoretical models and to study the relationship between worker flows and jobs flows. Hires, quits, and layoffs exhibit strong, highly nonlinear relationships to employer growth rates in the cross section. Simple statistical models of these relationships greatly improve our ability to account for fluctuations in aggregate worker flows and enable us to construct synthetic measures of hires, separations, quits, and layoffs back to 1990.