2 / 13  BIS central bankers' speeches  Sources: ECB, ECB calculations.5 Event studies – which measure the impact of central banks’ bond purchases in a narrow interval around the time of the announcement – play a part in informing our view on the efficacy of our purchases.
But we also use model counterfactuals to complement the impact metrics that we derive from event studies, and to test whether or not the impact of our announcements endures beyond the very short term.