I've never really found looking at the 'average' (be it median or mean) experience to be very useful here, though.
In the UK something like 30% of homes are owner occupied with no mortgage. But at the bottom, millions are completely stuck struggling to even pay the rent, never mind even think about saving any money or getting the income multiplier / job security / deposit required to start along that path.
Far more relevant is how accessible the bottom rung is, and whether that top portion (and so the average) are simply propped up by legions of modern day serfs.
In the UK in particular I'd be happy to build a wooden shack on a bit of agricultural land near to some utilities, maintain it well and stay out of others' way. Capital costs would be incredibly low.
But then there are the costs of jumping through regulatory hoops. Or simply being shut down by a judgement that your society says you have to live in a city at ten times the cost, or else.
Our version of poverty is 'death by bureaucracy'. The welfare state has created a situation in which many are simply incapable of fending for themselves - and the results when the state turns its back (google for 'UK benefit sanctions' for more information) are truly despicable.
That was to get a base ground truth to establish that there was something to consider, and that I'm not babbling nonsense. If you have better numbers, I would be glad to see them. It's well known that housing sizes are going up in the US, and one of the associated terms is 'McMansion'. But name-calling like that makes for boring, go-nowhere threads.
While you attribute UK's 77sq.m/person to the "welfare state", the Dutch and Danish welfare states have 115 and 137 sq.m/person. (UK has 255 people/sq.km, the Netherlands 409, and Denmark 128, so it's not a simple matter of density which causes the difference.)
In Sweden, where I live, there's been a huge increase in the amount of space per person. In the 1940s, it was considered spacious for two parents and three children to live in a flat with a kitchen and 2 or 3 other rooms. (See http://poseidon.goteborg.se/sv/Sok-ledigt/Bostadsomraden/San... , "Trots sitt syfte är de flesta lägenheterna tvåor eller treor, vilket räknades som en rymlig bostad för en trebarnsfamilj på den tiden.")
So I don't understand your objection. You have no counter-evidence, you bring up the UK which has the worst history in this regard, and what information I can find does not back your statement that something as broad as "the welfare state" can be the issue for the UK.
Planning restraint, combined with the way that housing is subsidised directly (rather than say, giving someone money to spend on building a new home).
I have nothing against the welfare state - I'd rather see a citizen's income than the nonsense mash of policies we have at present, though.
It makes no sense to me that the state should subsidise rental payments to private landlords in perpetuity. We should be building homes and relaxing planning permissions.
How is "The welfare state has created a situation in which many are simply incapable of fending for themselves" not a statement against the welfare state?
In any case, you're derailing the conversation, and my working hypothesis is that you want to talk about your feelings rather than put any interpretable numbers behind it. What is wrong with my analysis enough that it should be considered not "very useful here", which is what you stated. What is your objection?
I don't exactly know the situation in Europe, but in Israel,many city councils aren't giving permits for building small apartments, because they prefer to attract well off population to their area.
And while it's true that some are spend without thinking on a house, there are plenty who would prefer a smaller house.
(2.63 now and 2.7 in the early 1980s. FWIW, in 1950 it was 3.37. See http://www.infoplease.com/ipa/A0884238.html and http://quickfacts.census.gov/qfd/states/00000.html .)
So something has changed to encourage people to buy larger homes for the same number of people.