On a monthly basis the IRS releases a huge file with summary data about all the charities in its Master File of Exempt organizations. The financial data is limited, but it's enough to show some broad characteristics of charities as economic players. The National Center for Charitable Statistics in turn makes the IRS master file data available for some standard queries, if you can figure out how to do it. Their lastest data is from January, 2006, and I've summarized it in a PDF file to download (67.8K).
The lastest data shows the same pattern: very large organizations account for most of the economic impact of the nonprofit sector. Less than 2,000 organizations with gross receipts over $100 million account for 63% of the income of all the organizations combined. About 11,000 organizations between $10 million and $100 million account for an additional 23%.
On the other hand, the 178,000 organizations with income under $1 million account for only 3% of the reported income. It's a much more pronounced disparity than the typical 80-20 rule: this is closer to an 80-3 rule.
There's a fundamental misunderstanding of this basic reality of charities. There's a persistent belief that because small organizations are so numerous, they must have an economic impact in the aggregate. But it just isn't so.
And there's Robert Egger, who makes flat out statement in his book Begging for Change that 25% of nonprofits are unnecessary. When you look at economic impact, 25% is a gross understatement. More than 90% of nonprofits could go out of business and there wouldn't be a noticeable impact on employment figures.