Update: While the following chart has gone viral, a more careful search has turned up significant questions about its veracity. See Politifact for more details. It is worth noting that two studies consulted by Politifact (one by the Institute for Policy Studies and the other by the Economic Policy Institute) confirm that the number for the United States is in the ballpark: CEO to worker pay ratios peaked above 500 to 1 around 2000, and currently are only 325 to 1 (in 2010).
From the blog Sociological Images:
Other factors too enter into the assessment of a just wage: namely, the effective contribution which each individual makes to the economic effort, the financial state of the company for which he works, the requirements of the general good of the particular country…and finally the requirements of the common good of the universal family of nations…
Mater et Magistra (Mother and Teacher) #71 John Paul II, 1981
Some of these factors do not seem to have been taken into account when setting CEO salaries that yield a 475:1 ratio.