Cost overruns and waste are not the same thing. Overruns can be caused by legitimate scope changes, material costs, or unforeseen conditions — and the $4 billion in construction overruns mostly falls in that category. What we're measuring here is different: spending that cannot be explained by any of those factors. A PR firm billed twice with no measurable output. IT vendors paid 100–112% over contract under four different names. Legal costs that doubled because contractors sue and almost always win. The conservative estimate of this unexplained spending is $540 million. The high-end estimate is $2.8 billion.