Abstract This paper evaluates the contribution of cross‐sector allocative efficiency to the productivity slowdown in the US during the 1970s and 2000s. We extend the framework of Oberfield (2013) to derive sufficient statistics for allocative efficiency and decompose aggregate productivity growth in a multisector economy. We find approximately two‐thirds of the productivity slowdown can be explained by the lack of improvement in allocative efficiency. Furthermore, data shows that increased sector‐level volatility is associated with the deterioration of allocative efficiency.