chapter  9
Variation of innovation rates among countries and over time: the First Hat-Shape Relationship
Pages 4

In this chapter the long-term rate of qualitative change continues to be the key economic variable to be explained. Although this rate is not observed directly, we have noted that under certain conditions the trend growth rate of output (or consumption) per manhour is its approximate indirect measure, and that this trend growth rate can also be taken to be a proxy for the rate of technological innovation itself.