This isn’t a new problem. Scholar Alan Reynolds noted clear back in 2001 that CBO’s flawed projection model often leads to inaccuracies, pointing out several inaccurate CBO projections in the 1990s. He noted their budget projections widely missed the mark even though they were made only 12 months in advance.
Longer-term projections can be problematic as well. CBO’s cost estimate of the 2002 Farm Bill was off by $137 billion. Six years later, they miscalculated the cost of the 2008 Farm Bill by a whopping $309 billion.
Beyond short- and long-term budget projections, CBO has also proven grossly ineffective at forecasting consumer choices. Nowhere is this more clearly seen than the Affordable Care Act.