Public Citizen contends its analysis of U.S. Chamber of Commerce donors confirms the perception that big businesses call the shots at Washington's largest lobbying organization.

Just 64 donors accounted for more than half of the $179 million in contributions to the chamber in 2012, according to Public Citizen's analysis of the chamber's Internal Revenue Service filings. Nonprofit organizations are required to report contributions of $5,000 or more to the IRS.

In all 1,523 corporations and individuals donated more than $5,000 to the chamber, accounting for $169 million of the chamber's contribution total of $179 million.

More than 40 donors gave at least $1 million.

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