ABSTRACT

The data might spuriously associate a structural change in air pollution control with a shift in the trend in visibility reduction brought about by the embargo. Because of the nature of the air pollution problem, the phrase "the structural causes of smog" and along with it the phrase "structural change in air quality" can each mean two different things. This chapter focuses on simple piecewise regression model. It examines two functions: a two- and three-piece regression equation for the cubic functional form. A two-piece and a three-piece model are compared to the one-piece, ordinary least squares results using the cubic functional form. The results of the cubic regression can be hypothesized to have a technical and institutional component. The additional feature of this type of model is that it can accommodate institutional effectiveness that itself changes over time.