and control projects look similar in the frequency of red flag appearances. And it is worth noting that the Africa transport analysis discussed in the introduction did not find that complaint contracts saw a higher rate of non-responsiveness.

**It should be emphasized that some of our red flags are applicable to different contracts –so that no contract could raise all red flags.** Some apply only to ICBs and some to NCBs.  Similarly, the red flags may suggest the potential presence of different forms of corruption unlikely to be occurring simultaneously.  For example, collusion between bidders that leads to very similar bids is unlikely to take place at the same time as negotiation between a single bidder and an official that drives a large wedge between the winning (corrupt) bid and the next bid.  Corrupt contracts may only raise a small proportion of possible red flags, then.

**Furthermore, it is obvious that there are potential benign explanations for all of our red flags** –long negotiations may be because of limited capacity or complex contract discussions, foreign companies may not be interested in bidding because of the nature of the work, and so on.  All of this suggests no simple relationship between the presence or number of red flags and corruption.

**Given those caveats, the average number of red flags per contract across our full sample is 2.4.** This is about one fifth of the maximum theoretical number of red flags we could see per contract.  If the same held true for all of the 67 red flags suggested in one recent publication on red flags, that would suggest about twelve red flags would be raised for the average project looking at that broader list of warning signs.  Figure 1 displays the distribution of red flags across all of the contracts in our database.  As can be seen, almost every contract exhibited at least one red flag.

**We assume that such a result suggests a high level of ‘false positives’ being created by the red flag system.** And we will see some evidence in favor of this benign interpretation in the rest of the paper.  Not least, out of 9 outliers with four or five red flags, only 3 contracts are from the potentially suspect group, the remaining contracts stem from the control group.<sup>5</sup>

**All projects saw a number of red flags raised –without concentration in potentially suspect projects.** Figure 2 displays the average number of red flags per contract in each project in our database.  Every project sees at least an average of 1.5 flags per contract. Again, our ‘potentially suspect’ projects (numbered six and seven) do not see a notably higher number of red flags per contract –indeed, project seven sees the second lowest average number of flags.  Here we have to repeat that our potentially suspect projects are only and precisely that.  We do not know if the public allegations of INT involvement are correct, and we do not know the result of any subsequent investigation.  It may be that these projects were completely uncorrupt or that only one out of many contracts were corrupted.  As a result, these results are far from conclusive.  At the same time, results were broadly similar across red flags at the contract level in the red flag analysis of Africa transport projects between INT complaint contracts and others, perhaps suggesting some

> 5 Using soft red flags, where the mean number of flags per contract is 3, out of 9 outliers with five or more red flags, only 2 contracts are from the potentially suspect group.

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