2014: 23,442
2013: 21,614
2012: 21,748
2011: 21,289
2010: 20,191
2009: 22,473
2008: 19,986
2007: 19,961
2006: 17,157
2005: 17,356
2004: 21,031
2003: 22,732
2002: 17,182
2001: 18,967
my final thoughts:
you could lose 100 games and average well above 20k if the stadium was downtown
you could be in a pennant race and average 30k+ if the stadium was downtown