The paper shows that the interaction between population and firm knowledge produces a non-monotonic change in the assimilation gap. The assimilation gap follows a convex curve experiencing an upward slope driven by imitation and the downward slope by knowledge spillovers. Changes in the characteristics of innovation shift its peak across time. The relative advantage and compatibility shift the peak towards the left and the complexity shifts it to the right. The model is tested in a simulated environment and offers insights into the differences in temporal trajectories of the various adopter groups.