It’s the most common tool law firms reach for to upgrade their practice — a fact underlined by a recent Legal Week article that showed that 2010 was the most active year yet for U.S. law firms hiring partners in the U.K.. And, yet, there is surprisingly little research on the ups and downs of hiring shareholders into your business.

Partly plugging that gap, the consultant Motive Legal last month produced research tracking the retention of partners hired in the U.K. over the last five years, covering 1,944 moves. While the results confirmed what many already suspected, it is nevertheless striking to see it in data form: 44 percent of those partners hired in 2005 were no longer with the firm that hired them by 2010. Even looking at the figures over a three-year time frame, 30 percent had quit between 2007 and 2010.