This is one of the findings of a joint EMA/FDA analysis comparing decisions on 107 new medicine applications at the two agencies between 2014 and 2016. The study also looked at applications for which the agencies had differing outcomes in terms of type of approval and indication. The most common reason for diverging decisions at the two agencies were differences in conclusions about efficacy. Differences in clinical data submitted in support of an application were the second most common root of divergent FDA and EMA decisions.
The EMA has more on their website.