The hypothesis that improved H-modes result from reduction of transport where low-order rational surfaces are sparse is investigated with the integrated core pedestal SOL model. A function which expresses this sparseness is defined and a strength of reduction is determined which reproduces the improvement in confinement observed in Asdex-UG. The same dependence then agrees approximately with JET results. In application to ITER, the improved confinement gives improved fusion performance only if additional neoclassical impurity accumulation can be reduced or eliminated.