nal speculation was severely restricted by the capital controls in place after Bretton Woods. According to the journalists Larry Elliott and Dan Atkinson, 1968 was the pivotal year when power shifted in favour of private agents such as currency speculators. As the key 1968 event Elliott and Atkinson picked out America's suspension of the conversion of the dollar into gold except on request of foreign governments, which they identified as the beginning of the breakdown of the Bretton Woods system. 
Criticisms of Keynes's ideas had begun to gain significant acceptance by the early 1970s, as they were then able to make a credible case that Keynesian models no longer reflected economic reality. Keynes himself included few formulas and no explicit mathematical models in his General Theory. For economists such as Hyman Minsky, Keynes's limited use of mathematics was partly the result of his scepticism about whether phenomena as inherently uncertain as economic activity could ever be adequately captured by mathematical models. Nevertheless, many models were developed by Keynesian economists, with a famous example being the Phillips curve which predicted an inverse relationship between unemployment and inflation. It implied that unemployment could be reduced by government stimulus with a calculable cost to inflation. In 1968 Milton Friedman published a paper arguing that the fixed relationship implied by the Philips curve did not exist. Friedman suggested that sustained Keynesian policies could lead to both unemployment and inflation rising at once – a phenomenon that soon became known as stagflation. In the early 1970s stagflation appeared in both the US and Britain just as Friedman had predicted, with economic conditions deteriorating further after the 1973 oil crisis. Aided by the prestige gained from his successful forecast, Friedman led increasingly successful criticisms against the Keynesian consensus, convincing not only academics and politicians but also much of the general public with his radio and television broadcasts. The academic credibility of Keynesian economics was further undermined by additional criticism from other monetarists trained in the Chicago school of economics, by the Lucas critique and by criticisms from Hayek's Austrian School. So successful were these criticisms that by 1980 Robert Lucas claimed economists would often take offence if described as Keynesians. Keynesian principles fared increasingly poorly on the practical side of economics – by 1979 they had been displaced by monetarism as the primary influence on Anglo-American economic policy. However, many officials on both sides of the Atlantic retained a preference for Keynes, and in 1984 the Federal Reserve officially discarded monetarism, after which Keynesian principles made a partial comeback as an influence on policy making. Not all academics accepted the criticism against Keynes – Minsky has argued that Keynesian economics had been debased by excessive mixing with neoclassical ideas from the 1950s, and that it was unfortunate that this branch of economics had even continued to be called "Keynesian". Writing in The American Prospect, Robert Kuttner argued it was not so much excessive Keynesian activism that caused the economic problems of the 1970s but the breakdown of the Bretton Woods system of capital controls, which allowed capital flight from regulated economies into unregulated economies in a fashion similar to Gresham's law phenomenon (where weak currencies undermine strong currencies). Historian Peter Pugh has stated that a key cause of the economic problems afflicting America in the 1970s was the refusal to raise taxes to finance the Vietnam War, which was against Keynesian advice.
A more typical response was to accept some elements of the criticisms while refining Keynesian economic theories to defend them against arguments that would invalidate the whole Keynesian framework – the resulting body of work largely composing New Keynesian economics. In 1992 Alan Blinder wrote about a "Keynesian Restoration", as work based on Keynes's