A Note of Optimism

From a new blog by University of Chicago economist Casey Mulligan:

In order to find good predictors of non-financial sector performance, and GDP growth generally, we look to the non-financial sector itself. One of those predictors is the profitability of non-financial capital, or the “marginal product of capital” as we economists call it. The marginal product of capital after-tax is a measure of how much profit (revenue net of variable costs and taxes) that each unit of capital is producing during, say, the last year. When the marginal product of capital after-tax is above average, subsequent rates of economic growth (and subsequent marginal products of capital) also tend to be above average.

Since World War II, the marginal product of capital after-tax averaged between 7 and 8 percent per year. During 2007 and the first half of 2008 – exactly the time when financial markets had been spooked by oil price spikes and housing price crashes – the marginal product had been over 10 percent per year: far above the historical average. Compare this to the marginal product of capital in 1930-33 (the years of Depression-era bank panics): 0.5 percentage points per year less than the postwar years and significantly less than in 1929. The marginal product of capital was also below average prior to the 1982 recession (in this case, far below average) and prior to the 2001 recession. Thus, the surprise was not that GDP continued to grow 2007-8 despite the bleak outlook from Wall Street’s corner of the world, but that GDP growth failed to be significantly above the average. More important from today’s perspective is that much capital in America continues to be productive, and that this will likely permit Americans to advance their living standards as they have in years past. The non-financial sector today looks nothing like it did in 1930.