As a mother of boys I have vaguely noticed that you don't see many teenage girls on bikes these days.
I cycled to my son's secondary school today to drop something off, and in the bike shed counted 40 definitely boy's bikes, 1 definitely girl's bike and 3 that could have been either.
Being able to get around on a bike gives an important measure of freedom and independence to teenagers IME (as a girl, and as a parent). It seems like just another important, fun, freedom-giving thing that girls are missing out on more than they used to.
Anyone got any idea why? What is preventing more girls cycling? Is it parents being more protective of girls/more willing to drive them places? Cycling (helmets?) having an image problem amongst girls?