How much of growth output can be accounted for by growth of inputs and how much is due to growth of productivity? This book is the most detailed attempt yet made to answer this question for Britain. Contrary to the impression left by some previous authors, productivity growth is found to play a relatively minor role: growth of inputs accounts for most of the growth of output. The wealth of data presented is also used to shed light on the "New Growth Theory," which claims that externalities and increasing returns are the engine of economic growth. This book finds that the evidence does not support these claims.