According to Anglican Diocese, the church I attend covers 8 suburbs in Canberra. According to the 2006 census data, the following people have indicated that they are part of the Anglican Church:
So according the to stats just over 5,700 people have freely identified themselves as an "Anglican", (remember this is not just as a "Christian" but specifically "Anglican"). On any given week our total church attendance is probably around the 500-600 mark, maybe about 10% of the total number. Now I know some people might be sick and house bound, some people might work shifts (although we do have mid week services and three on Sunday), on any given week some people might be out of town, but taking all that into consideration, I still think there are a lot of people fibbing on their census form.
To make things more interesting, a fair number, at least 30% of people who attend our Sunday night service, actually do not live in these suburbs. I also know that some people who attend our church put "Christian" down on the census form as they rather identify as a Christian first and Anglican second (or third or fourth...or ever). So even the people who do attend our church aren't included in these 5,700 people.
The Atheist Foundation of Australia have started a campaign to encourage people to mark "no religion" on their census forms. They encourage you to think about your belief and if you hold to the Nicene Creed. They say that if you don't, then sadly you are not a Christian and you should not say you have a religion. I think I want it to go even further, although a doctrinal test is a good start, and I want to say that even if you believe the Nicene Creed and do nothing about it, then maybe you should read James and then answer more honestly.
One group the atheists are trying to go after are the people who mark "Jedi" as their religion. According to Tom Frame, in the 2001 census the "no religion" margin remained steady from the previous census, but that didn't include the 76,000 people who said their religion was Jedi and so it should have actually risen a bit. Also if you say you are an atheist, agnostic, materialist, secularist, rational etc... they also do not get put into the "no religion" category. This campaign might make it harder to claim that atheism is on the rise if the "no religion" category grows, as some people who say they have no religion still believe in a god or "spiritual things" (whatever that really means).
I also think there is a bit of a historical issue here. Australian's for some reason or another have always identified with religion (Christianity in particular) despite having quite a bad attendance rate. Again from Tom Frame, in Brisbane in 1907 it had 354,244 people of which about 131,000 people said they were Anglican and although the combined seating of all the Anglican churches in that diocese could seat 23,145 people they actually only had a regular attendance of about 15,000. Even 100 years ago Australians were claiming to have a religion on the census forms while still failing to actually attend that church on a Sunday.
Every year there is a census the National Church Life survey also takes place. It is an op in thing and more Churches are not taking part in it, but in 2001 only 8.1% of Australians filled in the survey as you have to actually attend Church that day to fill in the form. The survey was represented by most (if not all) of the major denominations in Australia and was quite a big jump from the 68% of Australians who said they were a Christian on the census form in the same year.
I think it is a good thing that people are encouraged to think about what religion they really are. If anything my own church should start their own campaign and invite the 5,000 people in the local area who thinks they are part of church they don't attend to come back. It shouldn't be too offensive, as after all shouldn't someone who said they are part of the Anglican church appreciate someone from that church asking them to come along. If not, then why identify with it in the first place? A bit of honesty should never goes astray.
I'm even going to put this out there: I will gladly shout someone a coffee or a beer if they live in one of those suburbs above and who says they are an Anglican and yet do not attend a church, provided (yeah there is a catch) we can chat about their reasons for their answer on the census form.
A good book I have read on religion in Australia and the census form is Losing My Religion by Tom Frame. It is definitely worth a read.