A controversial phrase, which actually means little more than the lowest rate of unemployment at which the jobs market can be in stable equilibrium. Keynesians, encouraged by the Phillips curve, assumed that a government could lower the rate of unemployment if it was willing to accept a little more inflation. However, economists such as Milton Friedman argued that this supposed inflation-for-jobs trade-off was in fact a trap. Governments that tolerated higher inflation in the hope of lowering unemployment would find that joblessness dipped only briefly before returning to its previous level, while inflation would rise and stay high. Instead, they argued, unemployment has an equilibrium or natural rate, determined not by the amount of demand in an economy but by the structure of the labor market. This is the lowest level of unemployment at which inflation will remain stable. When unemployment is above the natural rate demand can potentially be increased to bring it to the natural rate, but attempting to lower it even further will only cause inflation to accelerate. Hence the natural rate is also known as the non-accelerating-inflation rate of unemployment, or NAIRU. At first, the NAIRU became synonymous with the view that macroeconomic policy could not conquer unemployment. It was often used to justify policy inaction even when unemployment rose to more than 10% of workers in industrialized countries during the 1980s and 1990s, even though economists’ estimates of the NAIRU differed hugely. More recently, economists looking for ways to reduce unemployment have started to ask whether, and under what circumstances, the natural rate might change. Most solutions have stressed the need to make more people employable at the prevailing level of wages, in particular by increasing labor market flexibility. Economists still disagree over what jobless rate at any particular point in time is the NAIRU, but nobody any longer thinks that the natural rate is fixed. Indeed, some think the concept has no meaning at all.