"Traditionally bisexual has been referred to romantic or sexual attraction to two, and no more than two, genders, specifically male and female. However, the term is increasingly being used to refer to a level of sexual fluidity in which an individual moves bidirectionally along a spectrum of sexuality. These new senses, accounts for attraction to people who do not fall within the gender binary."
More and more studies show new generations are identifying on the bisexual spectrum than ever before. About double the percentage of youth identify as bisexual, gay, lesbian or transgender than they did only four years ago, according to a study from the Public Religion Research Institute.
'The Americans who fought in World War II might have been the "greatest generation," but millennials are by far the gayest. The last major meta-analysis of the size of the LGBT population in the United States, produced by the Williams Institute in 2011, estimated that 3.5 percent of adults identify as lesbian, gay, or bisexual, and 0.3 percent identify as transgender.' Samantha Allen
It could be a cultural shift. These results show that more young people are openly identifying their orientation; culture clearly plays a factor in identity, this is visibly indicated by more people coming out and identifying themselves as such.