Boston teams have won 14.3% of the 4 major sports championships since 2000. 

70 total - (2017 NFL - TBD, 2005 NHL - Lockout)

BOS - 10 

LA - 7

CHI - 5 - (Blackhawks, Cubs, White Sox)

PIT - 5

SF - 5 - (Warriors, Giants)

NY - 4 

MIA - 4 - (Heat, Marlins)

SA - 4

the Rest - 26