Who's on first? That may sound like the opening to an old Abbott and Costello vaudevillian routine, but on Madison Avenue, it could well be the description of the routine jousting between the top agency holding companies for bragging rights to the world's largest digital advertising services organization. It's may be difficult to determine who is Abbott and who is Costello in the Madison Avenue version, but the jousting has mainly taken place between WPP chief Martin Sorrell and Publicis chief Maurice Levy, though Omnicom also claims to be No. 1. According to new estimates from Paris-based agency billings researcher RECMA, WPP currently is on first, with Publicis ranking No. 2 following its acquisition of Razorfish, and Omnicom is No. 3. Given Wall Street's penchant for all things digital, it's not surprising that the ad industry chiefs are so embattled on the digital turf. When Online Media Daily reported last week that Publicis' acquisition of Razorfish had given it the edge over WPP in global interactive agency staffing - the metric favored by RECMA to rank digital agencies - WPP executives called foul, and challenged the analysis, leading OMD to appeal to RECMA for a ruling on the matter. Based on its most current tabulations, RECMA co-founder Eudes Delafon says Publicis' acquisition of Razorfish from Microsoft moves it into the No. 2 rank, ahead of Omnicom, but still behind WPP by a comfortable margin. Here's how RECMA's current data nets out in terms of worldwide digital staffing: WPP: 11,855 Publicis: 10,901 Omnicom: 9,160 Interpublic: 6,006 Aegis: 3,663 Havas: 3,397 But Delafon says there are some caveats, and that the ranking depends on how you define each company's digital organization. While WPP does rank No. 1 in overall digital advertising workforce, when comparing "interactive and media branches only," Delafon says Publicis' VivaKi unit now ranks No. 1 with a 38% share of Madison Avenue's digital media market, followed by Aegis' Isobar unit (20%) and WPP's GroupM (20%). In a third comparison analyzing each holding company's media agency networks based on their "integrated interactive staff, as well as a portion of the group's partners staff according to a case-by-case methodology," Delafon says the organizations rank this way: Aegis' Carat: 1,303 staffers WPP's MediaCom: 1,243 Publicis' ZenithOptimedia: 1,220 WPP's Mindshare: 1,153 Publicis' Starcom: 1,108 Omnicom's OMD: 1,100 WPP's Mediaedge:cia: 988 Havas' MPG:802 Interpublic's Universal McCann: 537 Interpublic's Initiative: 520 Omnicom's PHD: 290 Aegis' Vizeum: 253 Havas' Arena: 137 Case settled for now, but these figures are based on 2008 estimates, so the ad industry might as well get ready for another round of digital agency jousting in about a month or so, when RECMA releases its first look at its new 2009 Interactive Agency Report.