1 Marianna Baggio PhD in Economics and Management XXVII Cycle Building trust in online auctions: TTP (third trusted party) information in an experimental setting 1 – Introduction Although auctions have been used for centuries as means for price-discovery their theoretical study is relatively recent. The first pioneering contribution is undoubtedly the work by Vickrey dated 1961. Since then, economists have developed a rich literature in auction theory looking into specific aspects such as: how auctions are affected by the number of auctioneers, uncertainty, information, risk preferences, violations of expected utility, asymmetry etcetera. An even more recent topic within auction theory is the analysis of on-line auctions. On-line auctions, or OLAs, are simply a transposition of the bidding mechanism to the digital world, specifically the internet. The very first web-based commercial activity linked to auctions was launched in May 1995 by Onsale, while in September of the same year eBay entered the market. Both companies saw the potential of the web in expanding the normal features of bids by removing the physical limitations of traditional auctions such as geography, presence, time, space, and a small target audience. Computers and internet allow for the access to a wider variety of auctioned goods and services, but also to specific tools such as automated bids, instant notifications and powerful search engines. Naturally OLAs also have some drawbacks which are generated by the same boundaries that they have expanded. First of all, the digital world consents individuals to change, modify or substitute their identity. Both sellers and buyers can have more than one identity, or they can create a new one if needed. OLA companies try to overcome this by means of peer ratings, evaluations and reports. Unfortunately this method is far from perfection: a subject with bad ratings will create