My answer to the Question.

If 55% of Americans are gamers then 55% of people in San Francisco's bay area
are also gamers.  The bay area's metro population is around 7 million while san franciso 
is home to about 800,000.  This means that up to 7 million could be in the bay area at any time
so up to 3,850,000 gamers could be in the area at any time while most of them don't live there.