This is the annual Roy Morgan "survey" of AFL supporters and membership.

http://www.roymorgan.com/findings/8088-afl-supporter-ladder-june-2019-201908160718

It still has its basic problem in that it is a survey, e.g If you survey people in NSW about their favourite team they will nominate the Sydney Swans.  So to extrapolate that to Australia-wide support of 1.1M supporters is simply ludicrous.  That their "supporter" numbers could drop by 6% in one year should tell them their methodology is wrong......however...

the best part of the article is the profile of the typical Melbourne Demons supporter:

"In 2019 the quintessential supporter of the oldest football club in the land is well-educated, Victorian, and with a diploma or degree under his belt. Yes, he’s more likely to be male than female. He’s a young parent under 35 years old with pre-school aged children and likely following in the footsteps of his Melbourne supporting parents ".....etc

Anyhow.....enjoy the read.....

After next week it could be GWS replacing the Swans with 1.1 million fans.