What Do the Different Measures of GDP Tell Us?

GDP is key to macroeconomics, yet different ways of defining and measuring GDP have particular purposes. This paper examines how total GDP can be conceptualized, dissected and studied and how these improve our analysis and understanding of the sources of economic growth. While each approach is useful, macroeconomic analysis is shifting from a short-term, recession-driven focus on managing aggregate demand to a long-term, supply-side perspective on the determinants of economic growth. This shift is likely to accelerate in the current environment of concerns about a “new normal” of slow growth, with the debate framed by supply determinants such as an aging labour force and whether technological innovations have been mostly exhausted. How one views GDP has important implications for policymaking. If today’s chronic slow growth is due to deficiency of demand, stimulative fiscal policies might be the proper response, depending on a country’s fiscal capacity to take on more debt. However, if the shortfall in growth is due to a lack of productivity growth, different policies might be appropriate that increase the efficiency of resource use or the rate of innovation. The point is that a more detailed understanding of each measure of GDP leads to better comprehension of why it behaves in a particular way in response to different economic circumstances. This knowledge will allow policymakers to make more informed decisions. The author reviews each of the different ways of looking at GDP and how they evolved in response to the needs of analysts. He summarizes the strengths and weaknesses of each and what can be learned by contrasting and combining them in analysis. In order the six are: • GDP by industry; • GDP by expenditure; • GDP by income; • The quantity equation; • GDP by input/output; and • GDP by factor input. For economists, the different optics for viewing economic activity lead to a more profound understanding of the process of economic growth. Good analysis and policy prescription often depend on finding the right optic to understand a particular problem.