Android has now overtaken Apple as the most retentive brand on the smartphone market.
UBS says that over time it believes this will "increasingly pose a headwind to Apple's ability to take share."
Th note added: "This can also be seen if we look at the destination of consumers who are switching OEM - in prior periods Apple would have been a net-gainer in this base but now the outlook is much more balanced which we believe is a consequence of the improved retention that has built up around the Android ecosystem."
Apple's retention rate has dropped in China in particular.
Apple is possibly a victim of the on-going trade tensions between the US and China, according to UBS.