ABSTRACT
American research on differential institutional effects is not only much more voluminous than the British research: it is also considerably more sophisticated in methodological terms. Thus although its results obviously cannot be directly applied to the British situation, they provide useful suggestive evidence concerning the kinds of differential effects which there might be, and the process which produces these effects. The failure of most of the British and all the American studies considered so far to control more than the change variables must therefore cast doubt on the validity of their findings. One important limitation of these various findings is that they merely indicate the different effects of particular institutions, without providing any explanation of what caused the differences. Such explanations are important if research is to provide a basis for reforming the system.
