Is the Occupy Wall Street famous 1% stable? Occupy Wall Street has a famous slogan "we are the 99%", refering to the "fact" that 1% of the people in the US take nearly the quarter of the national income.  However, this does not seem to consider that many people with extreme incomes have very variables revenues and have to borrow a lot from the private sector to finance their source of revenue, and that this revenue is unstable.  Are there any studies/data confirming that the 1% that has nearly 25% of the national income is in fact nearly composed of the same people year after year?  Any data that considers "permanent income" instead of "annual income"?
I've not see a strict analysis of the top one percent but I have seen an analysis of the top 400 tax payers, the very highest income taxpayers:


  Who are the rich? It depends who you ask and when. Since 1992, the IRS
  has tracked the top 400 earners in terms of adjusted gross income—the
  so called fortunate 400. ... Most importantly, this IRS report
  demonstrates there is a lot of income mobility at the top. Of all the
  filers who have made the list since 1992, 73 percent were on the list
  just once. Virtually no one remains on the list for all 18 years, but
  for privacy concerns the IRS did not report exactly how many did, if
  any. In last year’s report, just 4 people remained on the list for all
  17 years. This suggests that most top earners do not have a portfolio
  of big investments that can be cashed in year after year, but rather
  one big asset, such as a family farm or business or stock, the sale of
  which triggers a capital gain.


The Fortunate 400 By William McBride

A slightly more targeted answer:


  Considering those whose information was found in both years,
  approximately half  of taxpayers in the lowest and highest income
  quintiles remained in the same quintiles 20 years later. Nearly
  one-fourth of those in the bottom quintile moved up one quintile,
  while 4.7 percent moved to the top quintile. About one-fourth of those
  in the top 1 percent were also in the top 1 percent 20 years later,
  but nearly 70 percent remained in the top income decile. The overall
  results suggest that, while there is considerable persistence among
  observed taxpayers, there is also meaningful movement even within this
  narrow age cohort. Some taxpayers start from the bottom and move to
  the top and vice versa.


NEW PERSPECTIVES ON INCOME MOBILITY AND INEQUALITY
Gerald Auten, Geoffrey Gee, and Nicholas Turner (2013)