I am not well versed in macroeconomics, the advice Brad DeLong gives to his undergraduate students seems really interesting (link)
- At a time horizon of 0-3 years, be a Keynesian: the most important things are the fluctuations in unemployment, in real demand, and in capacity utilization.
- At a time horizon of 3-8 years, be a demand-side monetarist: you can assume (provisionally) that fluctuations in employment, real demand, and capacity utilization die out; the most important things are the fluctuations in the composition of real demand (investment vs. consumption vs. government vs. net exports) and in inflation- and deflation-causing nominal demand assuming (provisionally) stable growth of the economy’s productive capacity.
- At a time horizon of 8 years or greater, be a sane supply-sider: the most important things are the processes of investment in physical, human, and organizational capital that raise the economy’s productive capacity.
I wonder whether this type of advice is common, and whether these numbers are based on empirical evidence or if they are based on DeLong’s own individual judgment of the time frames in which those models are predictive.