The natural rate of interest, or r*, is generally defined as the risk free real interest rate that would prevail in the absence of nominal rigidities and business cycle fluctuations. The natural rate concept dates back at least to Wicksell (1898). This concept is important in macroeconomics for several reasons. First, it provides a benchmark for the monetary policy stance in the long run. Second, it plays an important role in asset pricing, as the long segment of the (real) yield curve is the sum of the natural rate and the term premium. Third, it matters for debt-sustainability analysis.