The Oxford Olympics Study 2016: Cost and Cost Overrun at the Games
  Given that Olympic Games held over the past decade each have cost USD 8.9 billion on average, the size and financial risks of the Games warrant study. The objectives of the Oxford Olympics study are to (1) establish the actual outturn costs of previous Olympic Games in a manner where cost can consistently be compared across Games; (2) establish cost overruns for previous Games, i.e., the degree to which final outturn costs reflect projected budgets at the bid stage, again in a way that allows comparison across Games; (3) test whether the Olympic Games Knowledge Management Program has reduced cost risk for the Games, and, finally, (4) benchmark cost and cost overrun for the Rio 2016 Olympics against previous Games. The main contribution of the Oxford study is to establish a phenomenology of cost and cost overrun at the Olympics, which allows consistent and systematic comparison across Games. This has not been done before. The study concludes that for a city and nation to decide to stage the Olympic Games is to decide to take on one of the most costly and financially most risky type of megaproject that exists, something that many cities and nations have learned to their peril. 
Bent Flyvbjerg, Allison Stewart, Alexander Budzier
q-fin.EC