This project was a review of the literature and research on the impact of worsening market housing affordability on the demand for affordable housing, private renting, new household formation, and regional variations in these impacts. The aim of the project was to produce a systematic review of the evidence by following the ‘rapid evidence assessment’ method. This was based on ‘readily available’ evidence identified by keyword searching of electronic databases and websites. The aim was not to be comprehensive, but to cover the majority of evidence, including major official reports and data sources.