The euro, taken in effective terms, remained quite stable throughout 2016 and early 2017. Only in April did an appreciating trend emerge. This has not been a straight-line appreciation, and three events have "boosted" the euro directly:
The first two of these three events caused the 10-year rate spread between the US and Germany to narrow from 200bp in early May to less than 180bp in late July, which pushed the euro upward against the US dollar. On the other hand, the euro's appreciation since late July is different, because the euro's effective exchange rate has increased despite a slight narrowing of the US/Germany rate spread.
The EUR/USD exchange rate has risen slightly since the Governing Council met on 20 July, particularly with the threats from Russia and Saudi Arabia on 24 July about the implementation of oil production cuts causing a spike in prices, but the top contributor to the rise in the euro's effective exchange rate was the pound's precipitous drop: the EUR/GBP exchange rate reached 0.92, which is now very close to historic highs, due to economic figures, which continue to disappoint, and a lack of clarity over the UK’s Brexit strategy. The Swiss franc's sudden depreciation should also be highlighted, with the EUR/CHF exchange rate moving from 1.10 in late June to 1.14 today.