Celibacy or cheating?

[timelets]

Note that the clergy had the lowest fertility rate. Is it because of the celibacy requirement? If I understand it correctly Anglican clergymen are not required to abstain from marriage.



http://www.24grammata.com/wp-content/uploads/2014/08/Malcolm-Potts-and-Martha-Campbell-24grammata.com_.pdf

upd:

On July 29, 1968, Pope Paul IV issued the encyclical Humanae vitae (Of human life) upholding the ban on birth control. Catholics all over the world were shattered. Theologians were dismissed, priests left the church, and bishops contrived Jesuitical ways of permitting their congregations to “follow their consciences.” After Humane vitae, the percentage of American Catholics attending mass on a weekly basis dropped from 71% to 50%. By the 1970s, the marital fertility rate for Catholic women in the United States was 2.27, almost identical to the 2.17 for non-Catholics.