There’s been a lot of discussion about the ABS decision to retain names and addresses in the Census until 2020 rather than deleting them more rapidly as in the past. Although the details differ, there’s been a dispute of this kind before every Census I can recall. Rather than debate the details, I’d like to think about the question: should the Census be compulsory, and if not what kind of requirement should there be?
I can think of three main reasons why we (Australians/the government/the ABS) might plausibly want to make Census participation compulsory. I’m not fully convinced by any of them
(i) Because we can. Historically, government agencies of all kinds have relied on compulsion simply because they are established by law. For example, public servants used to be banned from going on strike and teachers were shipped from one school to another at a whim. The military still works this way: the need for immediate obedience to orders in battle is taken to justify the use of this power in all contexts. Almost certainly, this contributes to high quite rates
(ii) The idea that a census is better than a sample, and that this superiority depends on counting everybody. The suspicions of the apocryphal critic who decried conclusions about the whole population derived from a sample of few thousand “and worse than that, a random sample” live on in most of us to some extent. But in fact the census can never be a complete count – around 2 per cent of the population is missed. Given that those missed are likely to be fairly atypical, the effect on aggregate estimates is probably comparable in magnitude to the standard error for a sample of, say, 10000.
(iii) The legal role of the Census in determining various kinds of allocations, most obviously electoral boundaries. Even if we were confident in a statistical sense, no one would be happy with the use of a sample of votes rather than a complete count in an election, and it makes intuitive sense to apply the same standard to a count used to determine boundaries.
Against this, the fact of compulsion creates costs and raises the risk that people will supply incorrect data. More fundamentally, the less compulsion we have the better.
Given all of that, my preferred policy would be to require everyone to complete the census form, but to allow an opt-out request, asking for the information supplied to be deleted except for the basic facts required to establish an accurate population count. My guess is that the opt-out rate would be very low, and that the 5-yearly fuss would go away.
As an aside, this is, pretty much, the situation we have with “compulsory” voting. You have to turn up and have your name crossed off, but there’s no compulsion to write anything on the ballot paper. So, simple laziness doesn’t give you an opt-out, but any genuine objection can be accommodated. This is, among other things, why I favor optional preferential voting.