A power law distribution for the powerful law firms paid by a law department?

An interview of John Oviatt, chief legal officer of the Mayo Clinic, turned up an interesting tidbit. He said you commonly recognize a pattern of concentration of spending by law departments: “[Y]ou see the number one law firm for many departments receiving in excess of 30 percent of the total outside counsel spend.” It would not surprise me to see that the next firm down the spending list gets approximately half that amount (15 percent?) and the third half again, and so on. That progression would make the function that describes the drop off in outside counsel spending by firm a power-law distribution.

If I knew how to identify a power-law distribution mathematically, I would be more confident when I refer to the function (See my post of Dec. 14, 2010: positive quarter-power law; Aug. 15, 2011: possible power-law distribution of law departments by number of lawyers; and Sept. 8, 2011: posts with lists exhibit power-law characteristics.). I have previously collected references to power laws (See my post of April 27, 2010: power-law distributions with 6 references.).