There are many things that puzzle me about law firms: Why are they so slow to embrace nonlawyer senior managers? Why do they spend so much time and money recruiting associates, but manage to lose so many of the people they want to retain? And finally, why do some firms think that big pools of nonequity partners make good business sense?

Let’s zero in on the nonequity partner issue. Their ranks are growing: There was a 5.7 percent increase in this group in 2011 alone (to 12,599). Last year they constituted 45 percent of the partners at the 168 Am Law 200 firms that report two-tier partnerships. Eleven years ago, they accounted for just 31 percent of the partners at the 150 firms that reported nonequity partners.