For still more perspective, the CBO recently analyzed its forecasting record and discovered that its revenue projections for five years into the future averaged 1.7% of GDP more than actual outcomes after adjusting for tax law changes. That is, the CBO’s average revenue forecasting error was an overestimate of 1.7% of GDP. Why the huge errors? In the CBO’s words, they’re explained mostly by “the difficulty of predicting when economic downturns will occur.” Yet, the CBO followed that revelation by continuing to lower its unemployment rate projections—to all-time record lows in last week’s report—and by persisting with its practice of not including a genuine recession in its outlook.
http://ffwiley.com/blog/2018/04/20/8-things-to-know-about-last-weeks-cbo-report/
