Labor market outcomes such as turnover and earnings are correlated with employer characteristics, even after controlling for observable differences in worker characteristics. We argue that this systematic relationship constitutes strong evidence in favor of models where workers choose how much to invest in future productivity. Because employer characteristics are correlated with firm survival, returns to these investments vary across firm types. We describe a dynamic general equilibrium model where workers employed in firms more likely to survive choose to devote more time to productivity-enhancing activities, and therefore have a steeper earnings-tenure profile. Our model also predicts that quit rates should be lower in firms more likely to survive, and should tend to fall during slow times, while job destruction rates should rise. These predictions, we argue, are borne out by the existing empirical evidence.