This paper has examined the different approaches used by courts to adjudicate liability when two or more individuals jointly cause the external damages.

It is to be expected that rational peole defend themselves against pollution externalities, at the very least through spatial separation from the source. Bu even in the simplist models, defensive generates nonconvexities, multiple optima, and inconclusive policy guidance. This calls into...

It is observed that many regulations specify the ratio of two variables, rather than the level of a single variable. This paper considers the design of such regulations.