Learning and Growth

In this survey, I discuss four sources of growth of knowledge: research, schooling, learning by doing, and training. In trying to disentangle what is important, I emphasize the following facts: (1) even the most advanced countries spend far more on adoption of existing technologies than on inventing new ones, and (2) countries frequently adopt 'dominated' technologies. These facts provide a useful background for evaluating the different theories. They will also sharpen the point that it is important to distinguish between technology and human capital. The conclusion is simply this: In generating world growth, the world's research outlays are an essential ingredient. But for most agents the decision determining growth is one of whether to adopt existing technologies. We have perhaps underemphasized this in our modeling so far. Moreover, the handful of models that I survey contains a bewildering array of diverse engines of growth, most of which are not based on any firm evidence.