The final attendance percentage based on PAC-12 conference home games.
Arizona          100%
Washington    76%
Colorado        74%
Oregon          66%
USC              65%
ASU              64%
UCLA            63%
Utah              58%
Stanford        54%
California      47%
OSU              43%
WSU              41%

Here's another reason the Beavers and Cougars weren't invited to a power 4 conference.  And the next two lowest on the list, Stanford and California, had to beg to join the ACC.