60 The NAO undertook a survey of the non-PFI population of public sector construction projects in England with a capital value of £20 million and above, to get an indication of the performance of construction outside of the PFI sector. While identifying the population of non-PFI projects and correct contact details for these projects proved challenging, the NAO did achieve a response rate of approximately 22 per cent from the total population of 225. This population is much larger than the PFI population over the same period of 2003 to 2008.
61 Results from our survey show 63 per cent5 of non-PFI projects delivered to timetable and 546 per cent to contracted price. These figures are not directly comparable with our PFI performance statistics for a number of reasons:
• The sectoral mix is not directly comparable among the two samples, as set out in Appendix 1;
• The distribution of projects over the six years whilst fairly even in the PFI sample is heavily weighted towards the later three years in the non-PFI sample; very few projects have responded that completed in 2003 to 2005;
• The level of detail received from non-PFI projects does not allow us to draw such strong or detailed conclusions; and
• The lower response rate for the non-PFI survey increases the chances of a misrepresentative sample; therefore wider confidence intervals are reported within the statistics.
62 Of those projects that were delivered later than contracted, 67 per cent were also delivered over the contracted price.
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5 Range this percentage is likely to lie within: 51-75 per cent. A range of values has been presented as those who responded to our survey were only a sample of the total population, therefore we cannot be certain the figures obtained are exactly those we would have obtained if every project responded. See Appendix 1 for full details.
6 Range this percentage is likely to lie within: 42-66 per cent.