This paper examines the role of allocative efficiency in the productivity slowdown in the US during the 1970s and 2000s. The authors extend the framework of Oberfield (2013) to measure allocative efficiency and decompose aggregate productivity growth in a multi-sector economy with or without input-output linkages. The results indicate that approximately two-thirds of the productivity slowdown can be attributed to a lack of improvement in allocative efficiency. Additionally, the study finds that increased sector-level volatility is associated with a decline in allocative efficiency. The paper uses JEL codes O47 and E23 to classify the topic.