The academic and practitioner literature on tax reform, and comments from several experts contacted in connection with this report, emphasise that improving the performance of tax systems is highly complex and context-specific, without simple or direct answers. Improvements are only likely to come from combinations of large and small changes made with close and detailed knowledge of particular circumstances. Case studies reported by ITC-OECD (2015) report many different elements to reforms and difficulty in attributing improved results. A joint IMF, OECD, UN, and World Bank Group report acknowledges that building tax capacity in wealthy countries “has been the work of centuries” and that “no easy or quick fixes for establishing broad fiscal capacity” should be expected, although “patient, focused reform can achieve a great deal” (IMF et al. 2016, pp. 10-11).