WASHINGTON (AP) — Dozens of tea party groups and other conservative organizations of the kind subjected to improper scrutiny by the Internal Revenue Service operate with small budgets and rarely displayed overt partisan activities.

The Associated Press reviewed the public tax filings by 93 such activist groups.

Tax law experts say that a few of the groups built million-dollar operations and political ties that could have been legitimate grounds for IRS investigation.

Only 21 of the 93 groups the AP reviewed reported annual gross receipts higher than $25,000 between 2009 and 2011.

The median income for all the groups was just $16,700 a year. That figure includes the nation's biggest tea party group, the Georgia-based Tea Party Patriots Inc. It took in $20.2 million in 2012.

Copyright 2013 The Associated Press.

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