I
created this table about the number of workers per billionaire because
I was wondering whether the top-top of the wealth distribution might be
based on an undiscovered law of commerce.
If there is a law it would read something like this: for every million people who participate in the labor force of an industrial society one will become a billionaire. That is pretty much what the table shows.
That is actually the average of workers per billionaire in twenty three industrial countries.
The interesting details are what you get after you take Hong Kong out of the table. Hong Kong is too high because the number of workers in Hong Kong is grossly understated. Hong Kong really uses much of the labor force in Qundong Province on the mainland.
The remaining countries with above average billionaires per million workers in order are: U.S., Israel, Switzerland and Sweden. From my experience these are the most entrepreneurial industrial societies.
The two countries that should be at the top but
aren't are Holland and Japan. Holland may suffer from the fact that
many of their billionaires live elsewhere so they are less visible in
their home country. The U.S. probably benefits from the billionaires
who come from Holland, from several small countries and from Australia. Very wealthy people often want to live immersed in the vitality of the U.S. 
Japan is a different story. In Japan, like Holland, the nail that sticks up gets hammered down. I think Japanese culture tends to keep the top wealth hidden in the structure of Zaibatsu and maybe some of the wealthy people are still recovering from the economic disaster of the 1990s.
The data for this table should be looked at as a static photo in a dynamic world. The cut off of $billion is arbitrary. Many countries are still growing and we have no idea how income distributions will look after many decades of growth.
The table comes from the 2005 Forbes International Billionaire report and from the CIA Fact book.