Under pressure to develop deep expertise as a way to differentiate themselves in a crowded legal arena, many lawyers have focused more and more on a narrow aspect of the law—data privacy for financial institutions in the E.U., say, or public-private partnerships in the transportation sector. Like law firms themselves, clients are facing a world that is increasingly volatile, uncertain, complex and ambiguous. Clients need outside counsel that can collaborate to solve their problems, but law firms’ increased specialization creates an unfortunate conflict, and many are leaving big money on the table as a result.

When firms get collaboration right—that is, do complex work for clients that spans practices and offices within the firm—they earn higher margins, inspire greater client loyalty, gain access to more lucrative clients and attract more cutting-edge work. Empirical research, based on millions of data records, including time sheets, billing records and personnel files across dozens of global firms, provides the quantitative evidence. This form of integrated client service, which often crosses practice groups and other silos, is what I call smart collaboration. It requires a radically more sophisticated approach than the self-serving cross-selling tactic that a lot of managing partners implore their lawyers to engage in.