According to The Telegraph:
The number of British people defining themselves as “bisexual” has jumped by 45 per cent in just three years, according new official estimates.
For the first time, more young people in the UK describe themselves as bisexual than gay or lesbian combined, the figures from the Office for National Statistics show.
It is the latest evidence pointing to a shift in attitudes towards sexuality, with increasing numbers viewing their own position as somewhere on a spectrum rather than it being a black-or-white question. [emphasis added]