This paper studies how firms contribute to the productivity growth of an industry over their lifecycle. We present a decomposition method that allows us to condition the components of productivity growth on the age of production units. We find evidence for a prolonged positive exit effect that mirrors market selection during the early stages of firms lifecycle. This effect is tightly related to the negative initial productivity effect of entry. We also find some evidence that productivity-enhancing reallocation of resources between firms is concentrated on the middle aged firms.