Monetary policy actions since 2008 have influenced long-term interest rates through forward guidance and quantitative easing - both "unconventional" strategies. We examine whether the effect of such actions on Treasury yields have passed through to private yields to a degree comparable to experience before 2008. In order to perform this examination, we propose a strategy to identify the comovement between Treasury yields and private yields induced by monetary policy when an observable representing policy changes, such as changes in the interbank rate, is not available, or when other systematic factors may be important. Our strategy implies that least squares regressions, even within an event window, can be misleading, and our empirical results find evidence for such misleading effects. Implementation of our instrumental variables strategy suggests that the movements in Treasury yields induced by monetary policy statements have passed through to private yields, but to a smaller degree than typical prior to the end of 2008. This may suggest that the effectiveness of unconventional policy actions in stimulating activity are attenuated relative to conventional policy actions.