Former student David Henderson makes this point clearly in a recent post at EconLog. He points out that many of the people in the top 1% are professionals whose positions are protected by laws that restrict entry and keep out the competition. Quoting Jonathan Rothwell, he notes,
For lawyers, doctors, and dentists-- three of the most over-represented occupations in the top 1 percent--state-level lobbying from professional associations has blocked efforts to expand the supply of qualified workers who could do many of the "professional" job tasks for less pay....Proportion of lawyers in the top 1 percent? 15 percent....[EE: Shakespeare comes to mind]...
Proportion of physicians and surgeons in the top 1 percent? 31 percent. ...
Proportion of dentists in the top 1 percent? 21 percent.
Please check either David's post or Rothwell's paper for explanation and details.
I might be tempted to add tenured university professors to the group. I know tenure isn't explicitly a statutory provision, but it has similar effects. I hope David will consider including them/us in his forthcoming research.
Interestingly, it isn't raw, nasty, big-corporation monopoly that David is talking about; it's monopolies created by gubmnt, particularly barriers to competition in the professions.
As Harold Demsetz once wrote many years ago [paraphrased from memory], "the major cause of monopoly is government."