My main message is that the ECB’s APP does appear to have triggered substantial capital flows across borders. But it is far from clear whether this explains the depreciation in the effective exchange rate of the euro. In fact, asset purchases affect the exchange rate in broadly the same way as conventional monetary policy –through expectations of interest rate differentials.
It would, in principle, be affected by secular changes in saving behaviour. That’s before we have considered the question of whether changes in interest margins (e.g. between cash and mortgage rates) or levels of indebtedness may have a bearing on it.