Da conclusão:
[...] "We have noticed the decreasing amount of successful admin elections and have formulated two hypotheses that could explain this phenomenon. Hypothesis A stated that new admins are elected on the basis of acquaintance of the voter and candidate. If this would be a valid explanation, we could conclude that the community of admins is becoming increasingly closed, which would be detrimental to the sustainable development of the Wikipedia.
Hypothesis B stated that new admins are elected on the basis of similarity of experience in editing various topics of the voter and candidate. Since voters are other active admins whose experience increases with time, their thresholds of accepting a candidate are likely to increase (as has been observed from the simple statistics of RfA votings)."
Tom