While the differences may look fairly small in percentage terms, note that the variance from one report to the next – for the same quarter – can be as much as 3.2 percent! This is remarkable, especially considering that this is not only equivalent to failing account for $460 billion, but is more than the average annual rate of GDP growth since 1973. When one realizes that the Advance GDP reports are a major datapoint upon which policymakers are basing their decisions, it quickly becomes apparent why those decisions so often go awry. For nearly half of the quarters since Q3 2007, the mere identification of what would be contracyclical policy varied depending upon which report it was, Advance, Preliminary, Final, or Revised. Note too that the Revised 2 report, represented by the blue bar, was not published until July 2009, therefore any decisions made in previous quarters were based on data that differed as much as two percent of GDP.