An exploration of the use of experimental economics techniques to model user motivation for participation, and to appeal to users in different ways to change participation. 

• Developed a theoretical model to analyze motives for contribution to online communities. Designed and carried out a survey of 400 MovieLens users to test the assumptions of the model and to develop practical models for classifying users into different motivational subgroups. Have designed (and will carry out) experiments involving eliciting more substantial contributions using cues targeted at users' motives. Goal of work is to test social preference and conformity theories.
• Theoretical analysis shows that:
• users who want to influence others contribute more ratings than users who only care about their own direct benefits;
• if some users are inequality averse, publishing the distribution of ratings will make user ratings converge to the mean of the distribution; and
•  when there are a large fraction of selfish users, the total amount of rating on MovieLens will be less than the socially optimal amount.
• Developed the first empirical economic model of user contribution to an on-line community based on a combination of factors including intrinsic benefit, user effort, and direct and indirect benefits.
• Validated the first experimental economics model of user contribution to an online community built on user utility derived from direct and indirect sources.
• Demonstrated experimentally the effectiveness of both conformity and inequality aversion in shaping the behavior of users in even a low-interaction, low awareness online community.
• A case study in how to conduct experimental economic experiments in an online community using a combination of behavioral and survey data. 
• Found that both conformity and inequality aversion affect user behavior, but in different ways.  Conformity worked as expected, leading lower-contributors to increase their contribution.  Inequality aversion steered high-net-benefit users towards higher-effort (more altruistic) activities.  Findings are still being analyzed and will be submitted as a paper in the near future.

Title	Authors	Appears In	Publication Date	Date added
An Economic Model of User Rating in an Online Recommender System	F. Maxwell Harper, Xin Li, Yan Chen, and Joseph A. Konstan	Proceedings of The 10th International Conference on User Modeling	2005	01.28.06