The combination of output optimism and inflation pessimism during the latter part of the 1960s and the 1970s was a recipe for high volatility in output and inflation - that is, a set of outcomes well away from the efficient frontier represented by the economy’s Taylor curve.
Notably, the belief in a long-run tradeoff between output and inflation, together with an unrealistically low assessment of the sustainable rate of unemployment, resulted in high inflation but did not deliver the expected payoff in terms of higher output and employment.