In the Kyoto Protocol, Annex I countries are subject to caps on emissions, but non-Annex I countries are not. Barker "et al." (2007) assessed the literature on leakage. The leakage rate is defined as the increase in CO2 emissions outside the countries taking domestic mitigation action, divided by the reduction in emissions of countries taking domestic mitigation action. Accordingly, a leakage rate greater than 100% means that actions to reduce emissions within countries had the effect of increasing emissions in other countries to a greater extent, i.e., domestic mitigation action had actually led to an increase in global emissions.