Stephen M. Miller (Center for Business and Economic Research) recently published a paper "Output Decomposition in the Presence of Input Quality Effects: A Stochastic Frontier Approach" in the German Economic Review with Yasmins Rim Limam, Universite de Carthage & IPEG, and Giampaolo Garzarelli, Sapienza – Universita di Roma & IPEG and University and Witwatersrand. The paper addresses the question of how physical capital accumulation and total factor productivity individually add to economic growth.