Another way of describing the NRU is that it marks that level of UE that makes workers content with the real wage growth that their enhanced productivity makes possible. The growing bargaining power (relative to employers) of labour between 1945 and 1980 meant that the underlying NRU was increasing commensurately, perhaps to as much as 5.5%. It is deeply ironic that Keynesian demand management led inexorably to a much higher NRU.
