The hypothesis of non-jointness in input quantities (separate production functions) is well-known, and it plays an important role in many areas of economics. In this paper we define three additional forms of non-jointness which have received little or no attention in the literature, and which might be relevant for the firm as well as for the representation of the aggregate technology. We characterize all forms of non-jointness in terms of variable profit and joint cost functions. This yields a number of restrictions which are all testable empirically.

In this paper we estimate oil and nonoil import demand functions for the United States under the assumption that import prices are uncertain. Both import demand functions are formally derived from an expected utility maximization problem, treating imports as inputs to the technology. The model allows us to test for risk aversion and to assess the impact of uncertainty on the volume of imports, gross output, and the distribution of income. We find that uncertainty leads to a reduction in welfare, imports, and gross output. Moreover, it hurts labor relatively much more than capital. The impact of uncertainty, however, is found to be quite small.