Gavin - back to arguing with yourself are you - a bit like playing with yourself in the bath really!
Yes, you are absolutely correct, the data you present does have absolute political correlations.
The drop through the 1990's reflects the continual reduction in the ability to borrow housing development funding by Councils, owing to the Tory Government changes to local government finance rules - effectively prohibiting social house building as part of their ideological hatred of social housing.
The terminal output through the Blair blue-Labour years is evidence of how the working classes were sold out by Labour who simply carried on with the Tory policies inherited - and the same is true in so many other policy areas too.
The sudden increase in 2010 is the outcome of Brown having his eye opened to the massive folly of the previous 20+ years and the outcome of feeding house inflation by restricting supply whilst expecting the private sector to fill the gap. The return to Council House Building launched in 2008, implemented in 2009, delivered starts in 2010 and delivered many more in 2011.
The next correlation is the dismal outcome this year. The only bright figure to be reported next month will be the large increase in completions as the last properties from the Brown push are counted.
Meanwhile, your bathmate Shapps has turned off the social housing tap all together.
Nice friends you have Gavin!