Free childcare and parents' labour supply : is more better? / Mike Brewer (ISER, University of Essex, IFS and IZA), Sarah Cattan (IFS and IZA), Claire Crawford (University of Warwick and IFS), Birgitta Rabe (ISER, University of Essex) ; IZA, Institute of Labor Economics. Bonn, Germany : IZA Institute of Labor Economics, December 2016