In this paper we show how moving from the neoclassical model to the more recent endogenous growth paradigm can lead to markedly different interpretations of the same growth accounting data. In neoclassical theory, even if between 30 and 70 per cent of the growth of output per worker in OECD countries can be 'accounted for' by capital accumulation, yet in the long run all of the growth in output per worker is caused by technological progress. Next, we develop a hybrid model in which capital accumulation takes place as in the neoclassical model, but productivity growth arises endogenously, as in the Schumpeterian model. The hybrid model is consistent with the empirical evidence on growth accounting, as is the neoclassical model. But the causal explanation that it provides for economic growth is quite different from that of the neoclassical model.