I have an new article in the Washington Post where I make the case against secular stagnation. My argument is based on three observations. The details of these arguments and evidence for them are spelled out in the piece, but here is a quick summary.
First, the prima-facie evidence most secular stagnation advocates point to is misleading. They see the long-decline of real interest rates since the early 1980s as supporting their view. Their real interest rate measures, however, do not account for a trend decline in the risk premium. Once that is done there is no downward trend in real interest rates. And this measure--the 10-year real risk-free interest rate--is the one at the heart of the secular stagnation story.
This long-run measure of the natural interest rate is currently negative, but only because of the current slump--its deviations tracks the CBO's output gap--and appears to be simply deviating around a roughly 2% trend. Based on this evidence, there is no reason to believe it has permanently turned negative.
Second, claims about a trend decline in technical innovation and productivity growth are overstated. It is getting increasingly hard to measure economic activity with GDP in an increasingly digitized economy. This means productivity gets under measured. Moreover, there is reason to be believe we are on the cusp of a rapid growth spurt as noted by Erik Brynjfolsson and Andrea McAfee in The Second Machine Age: Work, Progress, and Prosperity in a Time of Brilliant Technologies. If so, the return to capital will rise and so will investment demand This should put upward pressure on the natural interest rate.
Third, the demographic outlook is not so dire. Baby boomers are no longer the largest U.S. cohort and around the globe the outlook for the prime-age working population is improving. This too implies a higher return to capital, more investment spending, and upward pressure on the natural interest rate.
One thing I did not get to fully explain in the article is why the growth of productivity and the labor force should affect the natural interest rate. To do this, we need to first recognize there was a trend and cyclical component to the 10-year real risk-free interest rate. This is equivalent to saying there is a long-term and short-term natural interest rate, with the latter gravitating around the former. So we need to distinguish how these different components are determined. Also, I left out a third determinant of the natural interest rate: household time preferences. My assumption in the article is that this part is relatively steady and all the interesting developments come from changes in productivity and labor force growth.
So with all that said, below is an explanation of long-term and short-term natural interest rate determinants. It is drawn from an earlier post:
[T]he long-term nominal natural interest rate is determined by trend changes in the expected productivity growth rate, the population growth rate, and household time preferences... Productivity matters because it affects the expected return to capital and expected household income. Faster productivity growth, for example, translates into a higher expected return on capital and higher expected household incomes. In turn, these developments should lead to less saving/more borrowing by firms and households and put upward pressure on the natural interest rate. The opposite would happen with slower productivity growth. Population growth matters because it too affects the expected return to capital. More people means more workers and output per unit of capital. For example, the opening up of China and India's labor supply to the global economy, meant a higher expected return to the global stock of capital over the past decade. That should put upward pressure on interest rates and vice versa. Finally, for a given level of expected income, a change in households time preferences means a change in their desire for present consumption over future consumption. This, in turn, affects households' decision to save and borrow. If households, say, start living more for the moment there would be less saving, more borrowing, and upward pressure on the natural interest rate.
Some like Paul Krugman and Larry Summers believe these determinants have changed enough such that the long-term nominal natural interest rate has been negative. I am not convinced and hope to explain why in a subsequent post (if you cannot wait, see my views in this twitter discussion). In my view, then, the important question is whether the short-run nominal natural interest rate has been negative since the crisis started.
So what do we know about the short-run nominal natural interest rate? It is shaped by aggregate demand shocks that create temporary deviations of the economy above or below its full-employment level (i.e. output gaps). For example, a large negative aggregate demand shock that temporarily weakens the economy will put downward pressure on interest rates. This happens because firms do less investment spending and therefore less borrowing in anticipation of lower future profits. It also happens because households, particularly credit and liquidity constrained ones, save more and borrow less in anticipation of lower future incomes. In short, aggregate demand shocks that create output gaps will also push the short-run nominal natural interest rate in a procyclical direction. This is a natural process that allows the economy to heal itself. What is not natural is when interest rates are prevented from fully adjusting to their market-clearing levels. That happens when interest rates are pinned down at the ZLB. See this earlier post for a graphical representation of this ZLB problem.
I hope that helps. Be sure to read the article at the Washingont Post.