Discrepancies exist between aggregate and activity productivity measurements in the US construction industry. Multiple studies using aggregate industry measures suggest that construction productivity has declined over the long term. A longstanding problem with the aggregate measures concerns the difficulty of controlling for inflation so as to accurately measure real output. As an alternative, average activity productivity, measured by individual work activities, indicates that construction productivity has increased over the same time period. Activity measurement data have been collected for 200 construction activities over a 22-year time period from commercial estimation manuals used by contractors and owners to estimate the cost and time requirements for construction. This paper examines the discrepancies between aggregate and activity measurements and suggests possible reasons for their existence.