 More recently, social changes, especially an increase in student numbers, greater labour mobility amongst young people and a rise in immigration, added to the demand for rented accommodation, causing a second growth period in the last four years.With local authorities unable to expand public rented housing to fill the gap and limited funding for Housing Associations, the newly private rented sector expanded in response to demand and grew by 27% in the fifteen-year period to 2004.In 2010 the government ran a large scale survey of the Private Rented Sector and analysed the social and economic spread of private landlords.