grey power

(chiefly Britain, Canada, Australia, idiomatic) The collective political, economic, and social influence of senior citizens, especially when they are mobilized by a common interest.

Example: 2002 Sep. 15, Luke Johnson, "The silver revolution is here," Telegraph (UK) (retrieved 28 July 2015):
  The outstanding example of grey power in action is the AARP—once known as the American Association of Retired Persons. This is probably the most influential lobbying set-up in the world.
2004 March 20, "Late 'bloomers' catch travel bug," Illawarra Mercury (Australia) (retrieved 28 July 2015):
  Grey power is increasing its influence over the world's tourism industry—and with a new nickname. If you're over 60 and have the time, the inclination and the funds to travel, you're now a "bloomer", according to a British holiday company.
2009 May 21, "It’s 1 a.m. Do you know where your kids are?," Macleans magazine (Canada) (retrieved 28 July 2015):
  If you needed any proof that grey power rules Maritime politics, check out the party platforms in the Nova Scotia provincial election. . . . Sure, dead people don’t vote, the party reasons. But pensioners do.