So-called tradable sectors, which produce goods for export and deal with foreign countries, include manufacturing, commodities, and services such as finance, law and engineering that compete globally. Non-tradable sectors such as government and healthcare and personal services have very little or no export or international output. This distinction comes from the Economist, April 30, 2011 at 34, which refers to a research paper on productivity in the two sectors.
It would make sense that law departments in tradable sectors would be larger because they would have export laws to observe, more specialists (such as privacy or antitrust), and possibly coverage in overseas offices. Non-US tradable companies would have more litigation managers, if only to deal with litigation exposure in the United States. In short, the sheltered sector of mostly domestic services would have less legal intensity, I would posit, than the sector buffeted by international competitors and global legal complexities.