As this book has proceeded, various arguments for protection have been considered and found wanting. If one ignores the beneficial effects of trade taxes on a country's terms of trade, there seems to be a good case for dismantling many existing protective barriers. However, even the well-motivated policy maker faces an enormously difficult task here. Pressure groups will strongly oppose tariff reductions, and the process of reform must, to some extent, accede to the political calculus. The political imperatives are important insofar as they prevent the immediate removal of all distortions. This means that the policy maker is necessarily working in a second-best world, attempting to reduce some distortions while others remain firmly in place. As we know from the theory of the second best (Lipsey and Lancaster, 1956; Meade, 1955a), such changes do not necessarily increase welfare. Moreover, the information required to identify and implement second-best policies is likely to be formidable. In a typical economy with many distortions, it would be helpful to have some simple rules telling us “which way is up”. Considerations of this kind have led a number of economists to look for simple “piecemeal” reform rules which can be readily understood and implemented by policy makers with some confidence that a welfare improvement will be the outcome. In this chapter we shall explore this literature in detail. The treatment is necessarily mathematical, and the non-technical reader will find this and the next chapter (which deals with similar issues in a multilateral setting) rather more difficult than the rest of the book.