Empirical results for other developed countries are reported in Sekine (2006). BIS Review 29/2007  5  regressions are themselves influenced by changes in economic conditions, changes in the underlying monetary policy regime are likely to be a source of changes in reduced-form inflation dynamics.
This problem is especially acute for structural relationships involving expectations or other factors that are not directly observable and so cannot be included in reduced-form regressions. In such cases, we cannot use the reduced-form equations to disentangle the effects of such unobserved factors – which themselves may be driven by changes in monetary policy – from that of other influences.