Some 15 years ago, searching for a consistent way to compare wages of equivalent workers across the world, Orley Ashenfelter, an economics professor at Princeton University, came upon McDonald’s.

The uniform, highly scripted production methods used throughout the McDonald’s fast-food empire allowed Professor Ashenfelter to compare workers in far-flung countries doing virtually the same thing. The company also offered a natural index to measure the purchasing power of its wages around the world: the price of a Big Mac.

Some of his findings are depressing. Real McWages — measured in terms of the number of Big Macs they might buy, declined over the first decade of the millennium widely across the industrialized world.

Even before the financial crisis struck, the McWages of McDonald’s workers in the United States, many Western European countries, Japan and Canada went nowhere between 2000 and 2007, a period of steady, though unspectacular, economic growth in most of the developed world. In the United States, real McWages actually declined.