Agreements to do so can be reached at the bilateral, regional or multilateral levels. The pursuit of food self-sufficiency to mitigate international risks is a costly policy that undermines the function of the international trading system, making markets thinner, more volatile and therefore riskier than if countries were to adopt open trade policies. In the face of both international and domestic risks, such as that of a failed harvest, a country which uses trade barriers to promote self-sufficiency because of the fear of trade interruptions may find itself exposed to greater potential losses than if it had remained open to international trade. At the national level, some developing countries may be vulnerable to imported instability, notably if their consumption is centred around just one or two food staples, and if their imports are sourced from just one or two countries. These risks can be mitigated by promoting more diversified diets (something that happens naturally to a degree as incomes rise) and by diversifying trading partners.