50
Singapore consumer watchdog sees doubling of complaints about lines on phone screens
(www.channelnewsasia.com)
From 14 to 31 is still pretty rare. (I checked, population is ~6mil).
And at such a low rate relative to the population, if you're assuming most cases don't report it, the difference in reporting could pretty easily be increased awareness that reporting it was an option or some other similar cause unrelated to an actual increased failure rate.