Here's the IRS pub that's the basis for the article: The 400 Individual Income Tax Returns Reporting the Largest Adjusted Gross Incomes Each Year, 1992-2009 http://www.irs.gov/pub/irs-soi/09intop400.pdf

The Tax Foundations take (http://taxfoundation.org/article/fortunate-400) is a little different. Interesting that in the 18 years that the report covers none of the taxpayers were on the top 400 list for all years. & only 4 (1%) were on the list for 17 years. 73% were on the list for just 1 year.... Their take was that most folks were on the list due to one time event...sale of assets, etc

Also wages were flat for all 17 years (as a % of total income). Partnership & S Corp income was up ~400%, which could be because of the growth in publicly traded partnerships.