The present paper seeks to elaborate an empirical analysis of the knowledge base of industrial sectors in the United States (US). Our broad objective is to distinguish sectors by looking at their repertoires of skills – that is, ability or proficiency in using and carrying out a set of tasks. In particular we set out to address these two questions:

1. Do different skill categories elucidate similarities and differences across sectors?
2. Do the skill bases of sectors undergo structural change over time?

These conjectures are probed empirically with an analysis of 290 industrial sectors in the United States over the period 2002-2010.