Why r* matters

In an interesting post, Eric Lonergen provides a nihilistic reflection on the relevance of r*. He points out that there's "no simple link between growth and real policy rates" when you look at cross-sectional global data, and that the habit of assuming the long run equilibrium real interest is 2% is lazy. I agree with his claim that the determination of r is "strikingly vague" and that the yield curve, the cost of equity, the term premium and credit spreads are important indicators that shouldn't all be subsumed into r*. But that is because r* is unique and important. 

He writes,

As a practitioner, and a global investor, I gradually came to the conclusion that demographic factors (notably youth dependency), GDP per capita, and changing risk properties were the most important variables in determining the centre of gravity for policy rates and government bond yields.

However consider the Beckworth/Selgin estimate of r*. They use a Ramsey growth model to define the real natural rate as the sum of productivity growth, population growth, and the household rate of time preference. Such factors are indeed the important determinants of "the centre of gravity", but that's exactly what r* is