Sums that just don't add up

In Gordon Browns opening speech as prime minister he made a reference to building three million more homes by the year 2020. Well, even I am not that good at my math but even I know at the rate of people needing homes in the future we will still be around 3.7 million homes short and that's an estimation of people needing homes at the rate needed today. With all the people we have coming to live here from EU countries and future generations having their children and so on, if you stop to think about things for a while it all just doesn't add up. Maybe this government and the previous ones should have made education a higher priority and math being a higher part of the education curriculum because adding up for many politician seems to be a problem.
What about all the social needed housing because as housing prices rise and they will keep on rising until this government intervenes. I do understand the economics and the value to any government to keep house prices high but what I don't understand is the over inflation.
Ordinary working class people are being priced out of the housing market and that where I think more help will be needed. We have a huge short fall in rentable accommodation in this country and we have a private sector that's taking full advantage of that fact and are charging rents that are overly inflated but if you are on government benefits then you simply will be lucky to get a place and that's becoming a problem and for once i don't have an immediate answer to the problem but I am sure the problem could be eased by not knocking down much needed housing to regenerate areas that really don't need regenerating.