Many in LGB community identify as bisexual
Researchers face challenges in estimating the percentage of the population that identifies as LGB. This is particularly true in the case of bisexuality, both because bisexuality has not been included in as many long-term surveys and because many bisexual people remain in the closet due to the social stigma. However, a 2011 report published by the Williams Institute of UCLA, which averaged the results of several population-based studies, found that 3.5% of the U.S. adult population identified as LGB. Of those who identified as LGB, just over half identified as bisexual.
Take a look at the full Williams Institute, UCLA School of Law survey findings.
Gates, G.J. (2011). How many people are lesbian, gay, bisexual, and transgender? Williams Institute, UCLA School of Law. https://williamsinstitute.law.ucla.edu/publications/how-many-people-lgbt/