# Predicting Reputation in the Sharing Economy with Twitter Social Data
## 2 Background
### Trust and Reputation in the Sharing Economy  
Sharing economy transactions have more significant risks involved than traditional online transactions as the relationships are more intimate and sophisticated (e.g., allowing a stranger to sleep in your house or entering a stranger's car). For these platforms to succeed, it is necessary that their users feel safe and trust each other when using them because without that safety feeling it is unlikely that people would want to expose themselves to such a danger: trust is a mandatory requirement for sharing economy platforms development. As stated by [PERSON] [58], _\"the success of these marketplaces is attributed not only to the ease in which buyers can find sellers but also to the fact that they provide reputation and feedback systems that help facilitate trust.\"_  
As mentioned previously, the notion of trust may vary in different domains, but, in the sharing economy, it can be defined as \"the psychological state reflecting the willingness of an actor to place themselves in a vulnerable situation for the actions/intentions of another actor\" [59]. To facilitate trust, sharing economy markets usually incorporate reputation and feedback systems [58]. After each transaction, users can provide feedback (e.g., five-star feedback score) and the market can derive the reputation of sellers and buyers from both public information (e.g., feedback) and not public information (e.g., messages). Reputation is only one of the available mechanisms to foster trust. Other mechanisms for fostering trust are long reciprocity in long-term relations, regulations, or professional qualifications [60]. In addition, personal reputation plays an important role in the shared economy [59; 61]. The presence of storytelling narratives, connected accounts, and photos can be used for verifying the digital identity and increase trust as well as the sense of personal contact. Moreover, some studies [39] have reported that consumers infer sellers' trustworthiness from their photos, and this visual-based trust and attractiveness could affect more than their reputation, although this conclusion has not been confirmed in other sharing economy transactions [62]. An interesting approach to improve trust in the sharing economy is the possibility of trust transfer across sharing economy applications. The term \"trust transfer\" has been used in different research contexts, but in the sharing economy [63], the trust transfer situation can be described as a trustor (e.g., a user) that has some initial trust on a trustee (e.g., a service provider in AirBnB) and transfers his trust on a different context (e.g., the same service provider in a different platform such as BlaBlacar). There are two main approaches to trust transfer in the sharing economy [63]: a direct trust transfer possibility from platform to platform, and providing a reputation board from a third party that acts as trust authority. A number of startups have proposed solutions for reputation boards (e.g., erated.co, mnicard.com, traity.com, truste.com), but they have not become popular yet. Reputation dashboards aim to aggregate users activity and reputation and to provide a trust score (or reputation passport) to become a trusted member in new social sites. In this work, the social site Twitter is used as the source for reputation data, and we aim to transfer this reputation to the sharing economy platform _Wallapp_ ([[http://wallappop.com](http://wallappop.com)]([http://wallappop.com](http://wallappop.com))) that is an online marketplace for second-hand articles launched in 2013. According to internal sources, the platform has more than 25 million downloads [64] and more than 5 million monthly active users in Spain, France, and US [65]. It follows the two-sided reputation schema, where both sellers and buyers receive a rating (from 1 to 5 stars) as well as an optional comment. Users' reputation can be measured by observing the ratings they receive after each transaction.