The early evidence on the importance of technological changes a source of the shifts in the relative demand for different types of labor during the 1980s came from case studies. The Bureau of labor Statistics conducted several case studies of the effects of changes in production processes in particular industries (Mark, 1987). In an industry that experienced a significant change in technology, the usual pattern was a dramatic reduction in the employment of production workers with an increase or no change in the number of skilled workers in that industry. More recently there have been several econometric analyses