Could gathering data on subjective well-being help governments and organizations develop policies that better serve the needs of their constituents? This book explores that question, focusing on the policy value of gauging "experienced well-being": peoples' moment to moment and day to day feelings of pleasure, contentment, pain and other emotions and sensations. This report identifies areas of policy and practice where such data would be useful -- ranging from city planning to custody policy to end-of-life care -- and discusses additional aspects of subjective well-being that are important for policy makers to consider. This report also assesses approaches for gathering these data, identifies surveys that should collect them on an experimental basis, and discusses methodological questions that remain.