Jenner & Block, a Chicago-based law firm that focuses on litigation, is shifting 15 to 20 of its equity partners to non-equity status, the National Law Journal reported Monday, citing anonymous sources.

Some of the partners are being asked to leave and a smaller number are opting for voluntary retirement, the legal newspaper said.

The firm's management last month began to move forward with the plan to cut some of the equity partners during the next year or two, according to anonymous sources cited in the Law Journal.

Though it eliminates the security of partnership -- once as honored as tenure at a university -- de-equitizing partners is a means to boost the average profits earned by equity partners to retain rainmakers and lure new talent. Equity-per-partner rankings have become the industry's measuring stick in the absence of any other accepted method, making demotions from partnership increasingly common.

In March Chicago-based Mayer, Brown, Rowe & Maw LLP announced its decision to purge 45 partners amid revenue growth of 11 percent in 2006. The conservative firm, one of the nation's 10 largest in 2006, topped $1 billion in revenues for the first time in its 125-year history. Sidley Austin demoted more than 30 partners in an effort to be more competitive more than eight years earlier.