**2. Improving tender design by allowing more time for bidding** . Short advertisement periods can lead to a lower level of competition and suboptimal tender performance, while they are also often corruptly abused to exclude non-connected bidders.

**Recommendation** : Limit the use of short advertisement periods so that potential bidders have adequate time to submit their proposals.

**Implementation** : Policy makers should directly influence advertisement periods by setting minimum required lengths and closing loopholes for short periods. Moreover, advertisement periods can be indirectly influenced by training contracting authorities on the importance of high-quality tender designs. Furthermore, guidance for suppliers on efficient preparation of tender documentation can help smaller companies compete. Related to these interventions, making full use of e-attestations (that is, the electronic storage and verification of certificates and other official documents) also allows to cut down the administrative burden of bidding and hence enables bidders to submit quality bids in a relatively short time frame. The implementation of such improvements in tender design could be closely monitored using real-time public procurement data and a dashboard of the type advocated earlier.

**3. Reducing the use of non-competitive types of procedures** . After 2016, there has been a significant increase in corruption risks due to the more frequent use of non-open procedure types in Bulgaria. Closed procedures, such as direct negotiations and awarding, significantly increase prices and often lead to contract implementation delays. One of the widely used corruption techniques is applying nonopen procedure types in an unjustified way, for example, splitting contracts so that the value of each part is below the threshold of the required open procedure. Although this practice does not necessarily aim at corruption rent extraction—institutions might use it to decrease the administrative burden by avoiding a difficult procedure—it certainly weakens competition and transparency and hence increases the risk of corruption. The implementation of such requirements could be closely monitored using real-time public procurement data and a dashboard of the type advocated earlier.

**Recommendation** : Increase the share of open procedures among all tenders to guarantee the broadest possible participation of bidders.

**Implementation** : The use of non-open procedure types can be decreased both through regulatory and capacity-building tools. National legislation can be amended to make it harder to use direct awards, negotiated procedures, and other non-open procedure types. For example, it is possible to lower the thresholds for the mandatory use of fully open tendering or amending the procedural requirements for invitations to tender, making them more open (for example, requiring the submission of four bids rather than merely requesting three bids). The use of central frameworks for widely used standardized goods such as office supplies could be further encouraged or made mandatory (Fazekas and Blum 2021). Training procurement officials on the use of pro-competition tendering practices, including the efficient use of open procedure types could further complement the above regulatory changes.

**4. Increasing the publication of calls for tenders.** We documented a sizable increase in the absence of call for tenders after 2016 which not only decreases transparency but affects corruption risks and market competition. If a contracting authority does not make a call for tenders publicly available, only connected bidders will know about the tendering opportunity. This corruption technique is strongly associated with using non-open procedure types, but it can also take place independently of them.

**Recommendation** : Require the publication of a call for tenders as well as the most essential procurement documents, in all or nearly all tenders.

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