Members of a birth cohort make decisions about childbearing and family formation in response to shared social and economic conditions. Dramatic changes in the social environment faced by cohorts over the late twentieth century, as well as changes in the composition of cohorts of U.S. women, have the potential to explain long-term trends in childlessness in the United States.
In other words, women do not make decisions about marriage and childbearing in a vacuum. They are responding to social cues all around them. On that note, one of the most important points she makes in the article, at least in my opinion, is relegated to a footnote:
Postponement is, of course, mechanically linked to childlessness: women who have an early birth cannot then be childless, and childless women are those who have avoided having children first at young ages and then at successively older ages. Research also suggests that intentions to be childless are rare at young ages, and most permanently childless women reach terminal childlessness by repeatedly postponing the first birth.
This is a key point--few women start out with a preference for no children--they arrive at the situation of childlessness a step at a time as they pursue the increasingly wide range of options open to them in modern western society.