An increasingly influential 'technological-discontinuity' paradigm suggests that IT-induced technological changes are rapidly raising productivity while making workers redundant. This paper explores the evidence for this view among the IT-using US manufacturing industries. There is some limited support for more rapid productivity growth in IT-intensive industries depending on the exact measures, though not since the late 1990s. Most challenging to this paradigm, and to our expectations, is that output contracts in IT-intensive industries relative to the rest of manufacturing. Productivity increases, when detectable, result from the even faster declines in employment.

We build a model of firm-level innovation, productivity growth, and reallocation featuring endogenous entry and exit. A new and central economic force is the selection between high- and low-type firms, which differ in terms of their innovative capacity. We estimate the parameters of the model using US Census microdata on firm-level output, R&D, and patenting. The model provides a good fit to the dynamics of firm entry and exit, output, and R&D. Taxing the continued operation of incumbents can lead to sizable gains (of the order of 1.4 percent improvement in welfare) by encouraging exit of less productive firms and freeing up skilled labor to be used for R&D by high-type incumbents. Subsidies to the R&D of incumbents do not achieve this objective because they encourage the survival and expansion of low-type firms.