A data rich study into IT project failure within the European Union by Dr John McManus and Dr Trevor Wood Harper can be found here.
They cite “total reliance on methodologies” as a cause of failure. This is interesting because you might think that adopting a methodology is a positive step, but they find that a methodology is adopted as a substitute for having experienced professionals in place.
It is also interesting to examine their data on when projects failed. Of course, this is a fairly small data set, but it is interesting to note how few projects fail at the testing or implementation phase. One might think that that would be the time when the rubber meets the road, and most failures would emerge, but it seems that either organizations are savvy enough to spot problems early, or to grin and bear it and redouble efforts at the later stage of the process when problems emerge.
Percentage Chance of Failure For Each Stage of the IT Development Lifecycle