Analysis is a tool for making important legislative and regulatory decisions but it is also a way of looking back to see whether decisions made in the past have been good ones. How well have legal rules actually worked in practice? Answering this question is crucial, not only for improving regulation and legislation in the future, but also for improving forward-looking regulatory impact analysis (RIA). This article was originally presented as the keynote address at the 22nd Anniversary International Conference of the Korea Legislation Research Institute in August 2012. It highlights what social scientists have told us generally about the role of analysis in decision making and why prospective RIA has been adopted around the world. It contrasts prospective RIA with regulatory impact evaluation (RIE), showing that even procedures that require prospective RIA can be properly subjected to ex post evaluation and that such evaluation is the only way to determine the true value of prospective RIA. It also explains the crucial connection between looking back and thinking ahead, concluding that without more and better retrospective research -- RIEs -- prospective RIAs cannot achieve their full potential over the long term.