VERTICALLY CHALLENGED? VERTICALLY RELATED POPULATIONS, EXIT RATES, AND THE EVOLUTION OF THE LASER PRINTER INDUSTRY.

The article discusses how the density of a vertically related population affects exit within a focal employee population. An analysis of the laser printer industry suggests that a focal firm's exit rate is influenced by the number of engine suppliers and the degree to which such suppliers sell their products on the open market rather than producing for downstream printer divisions. It is also suggested that exclusion of upstream density may generate omitted variable bias that influences the coefficient on downstream firm density. Differences between the density of vertically integrated and non-integrated laser printer firms are also discussed.