2011 eur still strong because SNB fixes franc against eur 1.2 in order to keep their export cheap, but its end on 2015 and made a flash crash on forex market that time, eur became weak. 2020 brexit finally happen, uk-as the second largest national economy after germany- leaving the euro zone, eur become weak again. now the best source of strength for eur is germany, as they represents 28% of the euro zone economy. so pay attention on germany economy data to know where eur price will go.