The future path of the federal funds rate is necessarily uncertain because economic activity and inflation will likely evolve in unexpected ways. For example, no one can be certain about the pace at which economic headwinds will fade. More generally, the economy will inevitably be buffeted by shocks that cannot be foreseen.

Financial market participants appear to recognize the FOMC's data-dependent approach because incoming data surprises typically induce changes in market expectations about the likely future path of policy, resulting in movements in bond yields that act to buffer the economy from shocks.

During the 1970s, inflation expectations rose markedly because the Federal Reserve allowed actual inflation to ratchet up persistently in response to economic disruptions - a development that made it more difficult to stabilize both inflation and employment.

Janet Yellen Quotes