Johnson argued that their fortune was generated to the greatest extent by Nathan Mayer Rothschild in London; however, more recent research by Niall Ferguson indicates that greater and equal profits also were realised by the other Rothschild dynasties, including James Mayer de Rothschild in Paris, Carl Mayer von Rothschild in Naples and Amschel Mayer Rothschild in Frankfurt.
Johnson berpendapat bahwa kekayaan mereka mencapai puncaknya karena aktivitas Nathan Mayer Rothschild di London; namun penelitian terbaru oleh Niall Ferguson menunjukkan bahwa laba yang lebih besar dan setara juga diwujudkan oleh dinasti Rothschild yang lain, termasuk James Mayer de Rothschild di Paris, Carl von Rothschild di Napoli dan Amschel Mayer di Frankfurt.