Major Legislation Costs Frequently Exceed Congressional Budget Office Projections

Legislators vote on bills based on projections that frequently miss the mark by wide margins when applied to major legislation. The Congressional Budget Office works directly with legislators during the bill-writing process, and its projections shape the resulting legislation. A report from Open the Books found the average error in CBO projections from 1983 to 2024 was 6%. The gap widens with the scale of the legislation. In 2009, the CBO projected a $25 weekly unemployment insurance bonus would cost taxpayers $39.2 billion over ten years; six years later, the office revised that estimate to $64 billion. In 2010, the CBO projected the Affordable Care Act would cost $788 billion. Two years later, the estimate ballooned to $1.76 trillion.