Australian Population (1999): 18,920,000
Australian Population (2009): 21,870,000
Percentage Increase: 15.60%
AFL Crowd Attendance (1999): 6,243,586
AFL Crowd Attendance (2009): 6,988,638
Percentage Increase: 11.93%
That seems to back Bollox up.
NSW Population (1999): 6,410,000
NSW Population (2009): 7,090,000
Percentage Increase: 10.61%
Sydney Home Game Crowd Attendance (1999): 335,930
Sydney Home Game Crowd Attendance (2009): 335,562
Percentage Increase: -0.11%
while those stats are good, keep in mind the level of immigration to Australia is so high that the majority of that growth is from people who weren't born in Australia and thus have no interest in AFL. Population growth amongst Australian born people is basically static.