How many new houses are built each year?

About 1.5m per year, however, this has declined due the economy.

http://understandingthemarket.com/?p=18

In 2005 1.6 million housing units where built. This includes single and multifamily units. In 2010 around 330,000 housing units where built. That is a decline of more than 300%. This is why it will take years before the housing market will be back to contribute to economical growth.