"We have delivered over 217,000 new affordable homes since 2010"—Conservative manifesto
"Fewer affordable homes are being built"—Labour manifesto
"The supply of affordable rented housing has been increasing"—Liberal Democrat manifesto
Three seemingly conflicting claims here: but actually, all three are reasonable. Taken alone they give part of the story, but together they provide quite a full picture.
Affordable housing sounds self-explanatory, but it's actually a technical term for a number of schemes to help people whose housing needs aren't "met by the market". It includes various forms of affordable rented housing; intermediate rent, which is priced above social rent but below market rent; and programmes promoting affordable home ownership.
According to the Department for Communities and Local Government, nearly 217,000 affordable homes have been delivered in England between April 2010 and September 2014. New affordable housing has been delivered at different rates in that time, though.
We use the term "delivered" for a reason: only 86% of additional affordable homes were newly built in 2013/14. The other affordable homes are acquisitions: mostly housing purchased from the private sector, or sometimes reclaimed from empty buildings.
While 217,000 may sound like a lot, the graph makes clear that Labour's claim of a decrease in affordable housing rings true, in the short term at least. The number has decreased from a high in 2010-11, although it was lower in the early 2000s.
The Liberal Democrat claim refers to the total number of affordable homes in existence, which of course is likely to be rising as more are delivered.
We don't actually have enough data to confirm that this is the case. The figures available don't show how many affordable houses are lost either through demolition or sales.