Methodology and sources

Appendix (report p. 25), global mean of 4,455 practitioners' estimates for projects completed in the prior 12 months: 57% finished within their initial budgets (so 43% did not), 52% experienced scope creep, 69% met original goals, 15% were deemed failures, 32% of budget lost when a project fails.

Appendix: 57% of projects finished within their initial budgets (3,234 respondents). Cover: the survey has been conducted since 2006.

Figure 2, Better Project Outcomes: projects completed within original budget 57% (2019), 59% (2020), 62% (2021).

US$135 million at risk for every US$1 billion spent on projects; 56% of that (US$75 million) at risk due to ineffective communications.

Copy of the full report hosted by Info-Tech Research Group. Modern Resolution, all projects, FY2015: 29% successful, 52% challenged, 19% failed (25,000-plus projects, FY2011-2015). Page 3: project size by CHAOS resolution (Small 61/32/7 through Grand 6/51/43). Agile versus waterfall table (39% vs 11% successful).

Sold by the Standish Group (digital edition, US$450). We have not read the report. The split it is quoted for (31% successful, 50% challenged, 19% failed) comes from secondary write-ups, so we label it as reported. The figures we have checked ourselves are the CHAOS 2015 ones above.

More than 5,400 IT projects; large IT projects (initial budget above $15 million) run 45% over budget and 7% over time on average and deliver 56% less value than predicted; total cost overrun of $66 billion across the sample; 17% go so badly they can threaten the company (black swans: budget overruns above 200%).

6,003 IT projects completed 2001-2017: cost overruns occur in nearly one in two public-sector projects against about one in three private-sector; the average public-sector IT cost overrun is nearly three times the private-sector average; 14% of public-sector projects exceeded budget by at least 100% (7% private); 59% of all projects completed within budget; one in 200 met budget, schedule and benefits.

1,471 IT projects: average cost overrun 27%; one in six was a black swan with a cost overrun of 200% on average and a schedule overrun of almost 70%.

5,392 IT projects completed 2002-2014: cost overruns follow a power-law (fat-tailed) distribution, so averages understate the risk.

Text: 98% of megaprojects suffer cost overruns of more than 30%; 77% are at least 40% late. Exhibit 2 (megaprojects in mining, oil and gas and infrastructure; sources: company annual reports, IHS Herold Global Projects Database, November 2013): the average cost increase is 80% of original value and the average slippage is 20 months.

Context only. It cites Flyvbjerg's nine-in-ten finding and gives McKinsey estimates of 35% average overrun for bridges and tunnels and 20% for roads. It does not contain the 98% or 80% figures; this site previously attributed them to it in error.

258 transport infrastructure projects in 20 countries on 5 continents, completed 1927-1998: costs underestimated in almost 9 out of 10 projects (86% likelihood that actual cost exceeds the estimate); actual costs on average 28% higher than estimated; rail 44.7%, fixed links (bridges and tunnels) 33.8%, roads 20.4% (Table 1).

The iron law of megaprojects (over budget, over time, over and over again); nine out of ten megaprojects have cost overruns; megaproject spending of USD 6-9 trillion a year, about 8% of global GDP; real-terms overruns of 80% for the Channel Tunnel, 200% for Denver International Airport, 220% for Boston's Big Dig, 1,400% for the Sydney Opera House.

Book; we have not checked these against the printed page. As quoted consistently: 16,000-plus projects, 47.9% on budget, 8.5% on budget and on time, 0.5% on budget, on time and on benefits (chapter 1); appendix base-rate table (around p. 192): IT mean overrun 73%, 18% of IT projects in the 50%-plus tail with a tail mean of 447%, nuclear waste storage mean 238%. The 2026 Public Management Review paper below cites the same appendix page for the nuclear-storage ranking.

Every Olympics 1960-2016 with data ran over budget, at an average of 172% in real terms. Table 3: per-Games sports-related cost overrun, real terms, for the 19 Games with valid data.

Table 1: 23 of 23 Olympic Games 1960-2024 with available data overran, mean cost overrun 159.3% in real terms (standard deviation 160.3%); Montreal 1976 overran by 720%.

Table 1 upper-bound capital expenditure uplifts: standard buildings 24%, non-standard buildings 51%, standard civil engineering 44%, non-standard civil engineering 66%, equipment and development 200%.

155 US Department of Defense contracts: the cumulative CPI was stable (range under 0.2) from the 20% completion point for 134 of the 155, and it usually got worse, not better, as the contract proceeded.