fertility factor
... that living in rural rather than urban areas is a fertility factor, associated with an increased number of children?
... that living in <a href="./Rural_area" id="mwBcg" rel="mw:WikiLink" title="Rural area">rural</a> rather than <a href="./Urban_area" id="mwBck" rel="mw:WikiLink" title="Urban area">urban areas</a> is a <b id="mwBco"><a href="./Fertility_factor_(demography)" id="mwBcs" rel="mw:WikiLink" title="Fertility factor (demography)">fertility factor</a></b>, associated with an increased number of children?