Well, this CBC article plugs the number somewhere between 100K - 200K, with around 250K people homeless at some point in the year. That's about 1%, and the numbers aren't that clear.
http://www.cbc.ca/news/indepth/background/homeless.html
I've heard the official estimates of around 600K - 700K in the US. I'm finding various links to that, but not any souce data, just reports from foundations and news sites.
There's estimates of about 700K in Great Britain
here's an article (PDF) - not sure of the source.


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