This paper documents a systematic shift in the nature of innovation in information technology (IT) toward increasing dependence on software. Using a broad panel of U.S. and Japanese publicly listed IT firms in the period 1983 to 2004, we show that this change in the nature of IT innovation had differential effects on the performance of the IT industries in the United States and Japan, resulting in U.S. firms increasingly outperforming their Japanese counterparts, particularly in more software-intensive sectors. We provide suggestive evidence that human resource constraints played a role in preventing Japanese firms from adapting to the documented shift in IT innovation.