"2018/19 saw the steepest year-on-year drop in the amount of broadcast TV watched by under 35s [in the UK] on the TV set"

"Changes in how people consume media continue to be rapid and profound, especially so among younger audiences.
2018/19 saw the steepest year-on-year drop in the amount of broadcast TV watched by under 35s on the TV set – down around two hours per week in a year to ten-and-a-half hours. By contrast, the time they spent using the TV set for purposes that include SVOD, YouTube and gaming increased again – up an hour a week to eight hours weekly. Music streaming by young adults also rose by around an hour a week to almost six hours weekly. Around the same proportion of under 16s now use YouTube each week as use the BBC (81%).
While these changes have so far affected young audiences the most, increasingly they impact the media behaviours of older audiences. For example, in 2018/19 more than half of over 35s used the TV set for purposes such as SVOD, YouTube and gaming and one in six used music streaming services each week.
Within this changing landscape, the time people spend with the BBC is trending downward year-on-year for both BBC TV and BBC Radio. The BBC is still the media provider that UK adults overall use the most, and audience performance for the year was within the target range set out in the 2018/19 BBC Annual Plan*.
91% of online adults used the BBC each week in 2018/19, in line with the target of 88-93%. UK adults spent 18 hours on average per week consuming BBC services, down on the year but within the target range of 17:15-18:45. They rated the BBC at seven out of ten, on average, in terms of their general impression, scored the quality of programmes and services at seven out of ten and value for money at five out of ten, all within target."
Source:  BBC Annual Report, July 2019