Integrating merged firms is never easy. But leaders at Arnold & Porter Kaye Scholer (APKS) and Norton Rose Fulbright may be attempting an especially tricky alchemy.

The allure of Kaye Scholer and Chadbourne & Parke to their respective merger mates is easy to appreciate. They’re both venerable, century-old, New York firms of a scale that seems manageable to absorb and with profit per equity partner (PPP) numbers that are accretive to the combined entities. With Kaye Scholer, Arnold & Porter is combining with a firm roughly half its size and with about 15 percent higher PPP. For Norton Rose, Chadbourne & Parke is about one-tenth its size and has almost twice the PPP. However, given Norton Rose’s verein structure, comparison with Fulbright & Jaworksi, the U.S. member of the verein, is perhaps more meaningful. The picture here is essentially unchanged: Chadbourne & Park is roughly 40 percent the size of Fulbright and has a 40 percent higher PPP (based on Fulbright’s pre-merger financial data adjusted for inflation).