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How big is the gap?
-  found that 16.1% of editors who started editing English Wikipedia during 2009 and who specified their gender were female.
-  used a propensity estimating strategy to approximate the gap estimated that the proportion of female U.S. adult editors was 22.7%.
- In Torres, N. (2016, June 2). Why Do So Few Women Edit Wikipedia? Harvard Business Review, "Jimmy Wales, the founder of the Wikimedia Foundation, which runs the site, said that the organization failed to meet its goal of increasing women’s participation to 25% by 2015, despite launching several initiatives."
Why is there a gap?
-  found that surveyed female Wikipedia users reported that fear of criticism made them less likely to contribute to Wikipedia.
What effects does the gap have?
-  shows:
- female newbies are reverted more than males;
- female editors are more likely to be indefinitely blocked;
- measurable gender-associated imbalances in the English Wikipedia’s content coverage quality.
What's the impact of activities to combat the gap?
- Lam, S. T. K., Uduwage, A., Dong, Z., Sen, S., Musicant, D. R., Terveen, L., & Riedl, J. (2011, October). WP: clubhouse?: an exploration of Wikipedia's gender imbalance. In Proceedings of the 7th International Symposium on Wikis and Open Collaboration (pp. 1-10). ACM. pdf
- Hill, B. M., & Shaw, A. (2013). The Wikipedia Gender Gap Revisited: Characterizing Survey Response Bias with Propensity Score Estimation. PloS one, 8(6), e65782. html
- Collier, B., & Bear, J. (2012, February). Conflict, criticism, or confidence: an empirical examination of the gender gap in wikipedia contributions. In Proceedings of the ACM 2012 conference on Computer Supported Cooperative Work (pp. 383-392). ACM. pdf