in 2009 the worldwide cost of failed IT projects was estimated to be as high as Six Trillion USD, using calculations by Roger Seasons.
Michael Krigsman was critical of these results and persuaded Gene Kim and Mike Orzen to relook at the numbers and make an estimate of the impact of IT failure on the global economy.
The statistics for project outcomes depend on whose results you read - the Standish Group conducts their Chaos Survey every two years and they show project failures to be around one quarter of the projects in their sample. The BCS published a study showing 23% of the projects they examined were cancelled.
In their calculations Kim and Orzen take a conservative 20% failure figure, and provide the following start for their calculations:
For just the Standard & Poor 500 companies, aggregate 2012 revenue is estimated to be $10 trillion. If 5 percent of aggregate revenue is spent on IT, and conservatively, 20 percent of that spending creates no value for the end customer - that is $100 billion of waste!
They continue to examine where IT money is spent and say
If we conservatively estimate that 50 percent of global IT spend is on "operate/maintain" activities, and that at least 35 percent of that work is urgent, unplanned work or rework, that's $980 billion worldwide of waste!
They conclude with a call to better management and less waste:
What reward can we expect through better management, operational excellence and governance of IT? If we halve the amount of waste, and instead convert it into 5x of value, that would be (50 percent * $1.2 trillion waste * 5x). That's $3 trillion of potential value that we're letting slip through our fingers!
The analysis can be found here.