Is a law partner an employee?

Often law firms force or "incentivise" partners into "senior status" when they reach a certain age. One New York firm has been sued by the EEOC on behalf of a 79 year old partner forced to give up his equity interest at age 70, and allegedly paid less than younger partners despite comparable or better billings and collections. Key issue: Are partners employees for purposes of ADEA? The New York Law Journal has background here.