First things first. In recent years, this survey of Connecticut law firm finances has been known as Trib 25, to reflect the number of firms that make the final cut. This year it's Trib 20. What happened? Are there fewer big firms in the state?

Not overall. But one significant firm dropped off the map in 2012. Levy & Droney disappeared after nearly 40 years in operation, with many of the lawyers moving to Rhode Island-based Hinckley, Allen & Snyder. Levy & Droney had been a fixture in the Trib 25, weighing in at No. 20 last year.

With a spot open, we set about researching additional firms that might step up. What we found were about 10 modest-sized firms that could be "contenders" for No. 25. The problem was, with our finite resources, we found it impractical to vet them all. And so we decided that rather than just guess, we would provide information this year on what we are fairly certain are the state's top 20 firms in terms of gross revenues in 2012.

We certainly don't mean to offend anyone, least of all the firms that have often been between No. 20 and No. 25 on our annual list — Neuberth, Pepe & Montreith; Levett Rockwood; McCormick, Paulding & Huber; and Zeldes, Needle & Cooper.

That said, nothing else has changed about this project and the methodology. The guidelines are set by our parent company, ALM, which sponsors such national listings as the Am Law 200 and the National Law Journal 350.

• Because the Trib 20 survey is entirely confidential, no firm's numbers are singled out as official or unofficial.

• In keeping with American Lawyer methodology, we have asked firms to distinguish between equity and non-equity partners. The vast majority did. In a few cases, the listings are simply our best estimate.

• The rankings for profits per partner and revenues per lawyer include only the firms that make the Trib 20. In other words, it's possible that there are lower-grossing firms that don't make the Trib 20 with higher profits per partner or revenues per lawyer.

How do we get the numbers? First of all, we ask politely, by letter. After years of experience with all the alternatives, many firms take charge of the process and simply provide them. In other cases, when only some pieces of the puzzle are provided, estimates can be formulated based on several known elements. All firms disclose how many lawyers they have, and we measure the head count on "full-time equivalence" basis.

Firms are also transparent about their first-year associate salaries, and the increases over the subsequent six to eight years follow a basic trajectory. Patterns emerge. We have created a software template that is useful in putting the pieces together. It's not rocket science. There are only so many hours a year a lawyer can work—or bill, and the law of averages has a stabilizing effect.

As with our sister publications' surveys, there is no disclosure of which figures listed above are official and which are our best-educated estimates. Over the decades, the level of firm cooperation in these well-read surveys has steadily and gratifyingly increased. •

• The Charts: Gross Revenues, Profits Per Partner, Revenue Per Lawyer