All the ONS has is a list of properties, even this is only partly accurate but for the sake of argument lets say it’s about 95% correct. Imagine a big street with numbers 1 – 200. All ONS officers can do is knock on the door of each of these houses that did not return a census form, perhaps 50 of these houses.Of those about 25 will answer on one of the 3 visits the ONS gets its staff to make. Those census forms are filled. That leaves 25 in a street of 200 that never fills out a census form. The ONS will make an estimate that perhaps 3 people live in the property that didn’t return a form.
So in one street roughly 12.5% of the population estimate is a guess. Multiply that by the huge amount of streets in the country and you can already see how the figures are inaccurate.
Now imagine the 200 properties I mentioned, how many people live in each, are they subdivided into bedsits, the ONS doesn’t know, did everyone who returned a form tell the truth regarding amount of people at their address (no they didn’t), has the property got unplanned accommodation attached somewhere (tens of thousands do).
Also there are large parts of London where the 12.5% of never returned Census forms would be heaven to the local ONS officers, it’s more like 30% unreturned and these are boroughs with populations of at least a couple of hundred thousand.
Several other things to consider. Large council estates with high density housing, make the unreturned census form level more like 50%. After the 2001 census 43 people were prosecuted for not returning census form as everything I’ve just told you is true on my sons life that is really a tiny amount of those not recorded, so pointless. I believe this time around 400 attempted prosecutions.
If we really wanted to know population the census would need to be supplemented by a) Use of NI numbers. b) Use of figures for those registered with GPs. c) Proper enforcement of law requiring response to census. d) Various other data such as that with DVLA Insurance company’s, satellite/cable TV, credit rating agencies etc.
Scary isn’t it?