Maintaining an adequate supply of teachers in the education sector is both a challenge and an area of significant concern. Of the teachers who qualified in 2013, 67.7 per cent remained in service after five years. The number of secondary school teachers has been falling since 2010 and the number of teachers leaving for reasons other than retirement has been rising since 2012. Coupled with the fact that the number of secondary pupils is increasing, and is expected to keep rising, this situation has placed intense pressure on teacher supply. Previous evidence shows that pay is deemed to be one of the most important factors influencing a teacher's decision to stay in a role, together with the workload and flexibility of working hours. However, up until now, no study has measured the relative importance of all the various factors that could influence teacher retention, nor quantified the impact that changes to these factors could have. To help fill this gap, researchers from RAND Europe analysed the evidence to better understand teacher retention and preferences. [For a related report, "Understanding Teacher Retention: Using a Discrete Choice Experiment to Measure Teacher Retention in England," see ED612733. This brief was prepared for the UK Office of Manpower Economics.]