Survey data from 2006 through 2008 shows that during those three years the number of matters handled by law firms and the number of firms used in the United States has remained relatively stable, at medians of about 350 matters and 100 law firms, respectively.
The survey, from Thomson’s Hildebrandt group, suggests that its law department respondents, generally fairly big companies, retain external counsel on roughly 30 matters a month. If so, they average about three matters per firm per year. Note also that it is a wide spread of law firms, suggesting that convergence has barely made a difference (See my post of Dec. 11, 2006: quixotic descriptions of work sent outside; and June 10, 2007: odd aspects of numbers of matters sent outside.).