Crowdsourcing for social contribution (supporting people with disabilities, public libraries) gained popularity as a new form of social participation. It is effective for people who have trouble working full-time, like the elderly. However, it is a challenge to motivate workers to maintain worker community. We propose a two-dimensional worker motivation model for socially conscious crowdsourcing, and develop a crowdsourcing system according to that model. 537 participants conducted more than 17 million micro-tasks in two years. We analyze workers' motivation based on their activities and questionnaire-based surveys. We divide workers into groups to find out which gamification elements or community functions efficiently motivate each worker groups.
