Analysis of time and cost data shows a good correlation between drift in project completion date and upward cost inflation. The causal effects in this relationship are complex and interconnected: cost drift may be driven by technical problems and schedule slip; it may be driven by deliberate re-profiling and with additional costs from standing overheads. Whatever the source, however, the implication of the analysis is that stretching expenditure over longer timeframes is likely to cause the costs to completion to grow, with no additional productive output associated with this extra cost (see Section 7.7).