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The figures are largely based on tax reports from fiscal year 2002, which runs from July 2001 to June 2002 for most nonprofits. One anomaly is the NonProfit Times's inclusion of Shriner Hospitals for Children. The charity suffered huge investment losses last year - $669 million. So Shriner's ranking is based instead on the $270 million it received in public support.
In addition, the chart omits certain types of nonprofits, including colleges, universities, and private foundations.
Finally, the main reason conservation groups devote such a low percentage of revenue to programs is that the IRS classifies money for land purchases as capital additions, not program expenses.