Actually, if Gambino is the second biggest, it's because the other three families (Bonanno, Colombo and Lucchese) are small and insignificant at this point, because Gambino has taken a thorough beating from the government and ny intelligence division. With acting boss John A. "Junior" Gotti arrested and in prison until 2004, and John Gotti Sr. about to die and terminally incarcerated, it's been reported that acting boss position has been passed over to Peter Gotti - the only brother not in prison (Gene Gotti was imprisoned for 25 years in 1989).
The profit Gambino was making in 1985 until Paul Castellano was estimated to be over $500m a year, while now it struggles to pull of 50$m. The size as decreased to 800-1000 made men to about 180-250. Carmine Agnello, husband to Victoria Gotti, was recently put in prison on RICO charges, he was a capo who made much of the family's money.