Though the regulatory landscape post-crisis remains far from fixed, contingent capital, or CoCos, appear likely to form part of policymakers' toolkits. There is undoubtedly widespread support from regulators the world over to have instruments that can be converted from debt to equity at times of financial market stress. Yet there is little consensus as to what the trigger for conversion should be.

Before looking at the question of designing the right trigger, it's worth noting why there is so