[...] Today, social housing--rented out at below market rates by councils and not-for-profit housing associations--is in many people's minds synonymous with housing people with low incomes. But it was not always like that--back in 1979, more than 30 per cent of people with incomes in the top half of the income distribution lived in social housing. By 2004, it was less than 10 per cent. Between those years, the supply of social housing available to let to new tenants each year dwindled--fewer new houses were built; property was sold off through the 'Right to buy', so that when occupants moved or died it was not available as social housing, and fewer tenants moved out of social housing or died.