Along with other recent research, Beauchamp and Pakaluk said, their findings "suggest that the first-order effect of the pill was to dramatically increase sexual activity, to the point that non-marital births actually increased."
"Thus, while the narrative about career participation may be true for some, even many, women, there have also been large-scale unanticipated and negative social consequences."
A "large increase in demand for abortion" was another consequence of the pill's introduction.
Beauchamp and Pakaluk's paper drew on previous research and on proposed theories about the impact of the contraceptive.
"In the past, some authors had suggested that the pill (and legalized abortion) may have played a role in rising female poverty by contributing to non-marital births-notably Nobel-laureate George Akerlof and former Federal Reserve chairman Janet Yellen in a co-authored paper with Michael Katz in 1996," they told CNA.
This argument was "primarily theoretical," said the researchers, who added that their own findings confirmed the "basic intuition" that fertility control might have unintended consequences.
"In terms of outcomes typically thought to be socially undesirable, we document that most of the increase in non-marital births due to pill access was concentrated among women from lower socioeconomic status households, and also minority households," Beauchamp and Pakaluk said. "We also show decreased chances of graduating high school for women who had access to the pill, consistent with the phenomenon of women giving birth as unmarried teens."
Research on the pill's impacts has lessons for both its critics and advocates.
"Advocates of the pill should give more thought to the habit-forming and behavioral consequences of using the pill," Beauchamp and Pakaluk suggested, comparing the situation to that of people being insured. "With good insurance we worry about moral hazard-the phenomenon that when risk is minimized or believed to be insured away, people take greater risks, essentially changing their behavior to become more risky. Some of this risk can then lead to adverse outcomes."
Advocates of the pill and other contraceptives should take these behavioral effects into account, "especially among the young who are still developing character," they said. These behaviors can turn into habits and compound effects over time.
There is still "a lot of 'casual' thinking about giving contraceptives to young people, with little regard for the behavioral consequences," the researchers said, although some advocacy for long-acting reversible contraceptives appears to be "substantially motivated" by concerns about the importance of behavior.
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Beauchamp and Pakaluk suggested that critics of the pill should recognize that its introduction and effects are complicated. They said many of its documented effects are associated with increased educational attainment and work opportunities for women.
"It is certainly not always the case that things which are morally dubious lead to observable or measurable negative consequences," the researchers said.
Pope Paul VI's 1968 encyclical "Humanae Vitae" upheld Catholic teaching rejecting contraception, including the birth control pill. However, the researchers noted that people largely failed to accept to teaching and "people today generally believe that our way of life is unthinkable without the pill."
"There are lots of fascinating things to learn from this kind of work, especially for the critics, because inside of this research may be clues to thinking about alternative ways to provide for the true human needs that people aim to satisfy using the pill," Beauchamp and Pakaluk told CNA.