The Olympics have the highest average cost overrun of any type of mega-project – something that, according to researchers from SAID Business School and Oxford University, should be a cause for caution for anyone considering hosting the Games.

In a state-backed report, consultants find the Boston 2024 bid’s costs to be underestimated and the benefits overestimated. Boston 2024 organisers say the report missed out on details and is flawed.

With the ten-year anniversary for the Athens Summer Olympics coming up, media fills with stories about the questionable legacy of these games featuring photos of abandoned Olympic facilities left to fade away while Greece is struggling to balance what is left of a broken economy.

Four years before the opening match, the 2018 FIFA World Cup in Russia has already produced significant cost overruns and construction work is falling behind deadlines. Overall, it looks set to become the most expensive World Cup ever, says Martin Müller from the University of Zürich in this comment piece.

The Olympic Winter Games cost on average five times more than the organisers indicate. This includes Sochi 2014, which also experienced a quintupling of their costs. The IOC wants this to change, but has been powerless for decades.

The budget of the Olympic Games in Sochi is higher than all the Winter Games from 1924 until 2010 put together. Sochi 2014 is estimated to costs around 40 billion euro, where the 21 previous Winter Games cost approximately 35 billion euro altogether, a large scale archival research project reveals.

If the size of the Olympics are not reduced, they may become awarded only to rich and authoritarian regimes in the future. Professor Jean-Loup Chappelet, sports governance expert at IDHEAP in Lausanne, analyses the risks of Olympic gigantism