evidence: The size of the social housing sector has been decreasing over time. The proportion of the population living in social housing in Great Britain halved between the early 1980s and early 2010s, according to the Institute for Fiscal Studies. The IFS puts this down to two key developments: the introduction of Right to Buy in 1980, which gave tenants the ability to buy their council houses at below market rates, and a general drop in the amount of social housing being built. [...] Social housing usually refers to homes rented at sub-market levels by councils and housing associations. "Social rent" levels are around 50% of market levels. The government also includes "affordable rent" homes in its definition of social housing, these are up to 80% of market levels.