this paper examines these relationships in more detail, and asks whether contributions, perceived benefits, and the relationships among them were different for owners of the lists (formal leaders), active posters, and lurkers of the groups, and for nonwork-related and work related groups. To test our hypotheses, we conducted repeated measures ANOVAs with respondent role (owner or other member) and group type (non-work or work-related) as fixed effects, and group size and content volume as covariates. Building 18 2 3 4 5 6 7 8 9 10 11 12 13 14 1 . T o t a l T i m e 1 . 0 0 2. Infrastructure Maintenance . 6 8 * * 1 . 0 0 3. Social Control .29** .28** 1.00 4. Social Encouragement .42** .29** .47** 1.00 5. External Promotion .31** .33** .29** .32** 1.00 6. Content Provision .87** .65** .29** .36** .28** 1.00 7. Audience Engagement .39** .11* .12* .16** .06 . 24** 1.00 9. Information Benefits .16** .05 -.10 .13* .00 .06 .15** .24** 1.00 10. Social Benefits .33** .17** .20** .35** .22** .28** .17** .30** .30** 1.00 11. Altruistic Benefits .28** .23** .10 .34** .15** .26** .13* .32** .28** .49** 1.00 12. Work-Related Group -.06 .07 -.09 .04 -.02 -.03 -.02 .28** .08 -.12* .09 1.00 13. Log (Group Size) -.01 -.11 -.02 .02 -.09 -.11* .10 .07 .20** -.08 -.05 .17** 1.00 14. Log (Message Volume + .01) .19** -.04 .08 .13* -.03 .08 .13* .06 .21** .08 .09 -.18** .52** 1.00 15. # of Members Known Outside the Group .14** .20** .06 .08 .07 .31** -.01 .06 -.06 .02 .12* .05 -.07 .01 Pairwise Ns range from 325 to 385 * p <= 0.05; ** p <= 0.01 Table 3: Correlations among measures 19 RESULTS A premise of this research is that community building requires significant expenditures of time and effort on the part of members. The descriptive analysis presented below shows that members reported inv...