The new year finds a new name atop the annual year-end lists of M&A legal advisers, with Skadden, Arps, Slate, Meagher & Flom topping three separate rankings of law firms based on the total value of their corporate clients’ M&A transactions in 2012.

The Skadden sweep—which the firm completed Friday when MergerMarket released its 2012 results [PDF]—comes a year after the firm placed third among M&A advisers ranked by Bloomberg, MergerMarket, and Thomson Reuters. As we reported last year, Sullivan & Cromwell, Simpson Thacher & Bartlett, and Wachtell, Rosen, Lipton & Katz, in varying order, topped the 2011 rankings.

As The Am Law Daily has reported in the past, each outlet relies on its own metrics in compiling the year-end M&A league tables. Those differences mean the lists’ greatest value lies in the broad perspective they offer about which firms are most active on the M&A front, rather than in their reliability as apple-to-apple scorecards.

(Thomson Reuters [PDF] released two separate rankings: one for deals announced in 2012 and another for deals completed within the year. Skadden topped both lists.)

Skadden is not alone among Am Law 100 and Global 100 firms occupying the three lists’ respective top tiers this year. In addition to Wachtell, Magic Circle firms—Clifford Chance, Freshfields Bruckhaus Deringer, and Linklaters—claimed the top-three spots in the 2012 rankings based on total value of global deals on which they advised. Rounding out the top five on the various lists were Cleary Gottlieb Steen & Hamilton, Latham & Watkins, Simpson Thacher & Bartlett, Sullivan & Cromwell, and Weil, Gothsal & Manges.

The three outlets also rank firms based on overall deal volume, with Am Law 100 firms Jones Day, DLA Piper, Latham, and Kirkland & Ellis topping the lists in that department.

Only one firm from outside The Am Law 100 and the Global 100 managed to earn a spot in all three outlets’ rankings: Canadian firm Blake, Cassels & Graydon, which showed up in the lower half of the three lists.

Skadden—whose $2.16 billion in gross revenue in 2011 earned it third place in The American Lawyer‘s most recent Am Law 100 survey— outpaced the competition in 2012 by representing clients on several of the year’s largest transactions, including the $28 billion deal announced last month that saw the firm advise a consortium of Russian oligarchs selling Rosneft the half of TNK–BP it did not already own. Skadden also had a role representing Anheuser-Busch InBev on its $20.1 billion purchase of the remaining 50 percent stake in Grupo Modelo last summer, and led the way for Sprint Nextel on the $20.1 billion sale of a 70 percent stake in that company to Japanese telecom SoftBank in October.

While the three transactions accounted for just a portion of Skadden’s M&A work last year, they represent a diversity of industry and geography that New York–based M&A partner Howard Ellin believes extended throughout the firm’s M&A dealings, large and small. “Skadden’s practice in 2012 not only covered high-dollar-value transactions, but covered a broad range of transactions across every industry and geography, and we are extremely proud of that,” Ellin said in a statement.

Dealmaking wasn’t easy for anyone in 2012, with Bloomberg [PDF] noting that last year’s total global deal value of $2.23 trillion was down 7.85 percent from the previous year’s total of $2.42 trillion. (As we noted last year, Bloomberg reported that the total global value of deals in 2007, before the economic downturn hit, reached $4 trillion.)

Ellin and fellow Skadden M&A partner, Stephen Arcano, said in a statement that they remain “cautiously optimistic” that M&A activity could increase in 2013. Arcano said he sees “a number of reasons to believe we could see takeover activity build in 2013,” while Ellin warned that ongoing economic uncertainty could dampen the confidence of corporate executives when it comes to weighing transactions.