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Editor’s Note: Nina Brooks is a PhD candidate in environment and resources at Stanford University. Eran Bendavid is an associate professor of medicine at Stanford University. Grant Miller is an associate professor of medicine at Stanford University, director of the Stanford King Center on Global Development, and a non-resident fellow at the Center for Global Development. The opinions expressed in this commentary are those of the authors. View more opinions on CNN.

(CNN) —  

Few public policy issues are as divisive as abortion – and to think that all sides could agree on even one aspect would seem naive. But based on our analysis of global data spanning two decades, we argue that there could yet be such an instance if we were to take the evidence seriously.

Our findings published in The Lancet Global Health last Thursday suggest that a major US global abortion policy has striking, important, and unintended consequences in sub-Saharan Africa.

Nina Brooks
Courtesy of Nina Brooks
Nina Brooks
Eran Bendavid
Eran Bendavid
Eran Bendavid
Grant Miller
Rod Searcey
Grant Miller

The Mexico City Policy, also known by detractors as the “Global Gag Rule,” was first introduced in 1984 by the Reagan administration at the United Nations International Conference on Population and Development, held in Mexico City. It prohibits private organizations from advocating abortion either explicitly or implicitly – through counseling, referral, direct provision, or lobbying for policy or legal reform, as a precondition for receiving US federal family planning funding. Under the earlier Helms Amendment, organizations already could not use federal funds directly for abortion – although funds are, of course, fungible.

In practice, the policy largely affects lower-income countries where these organizations are major providers of family planning and reproductive health care and rely heavily on US support. Since its inception, every Democratic president has rescinded the policy, while every Republican who has entered the Oval Office has reinstated it with an executive order within the first few days after inauguration.

Perhaps predictably, some organizations comply, while others don’t, forgoing financial support from the US. Those experiencing financial shortfalls generally seek alternative sources of support, but the magnitude of aid provided by the US is so great that other sources typically cannot compensate. The on-again, off-again policy therefore results in a financial roller coaster for organizations that are important providers of other basic health services.

Anecdotes about the consequences of the Mexico City Policy abound, although they take on a predictable slant depending on who you ask. However, there has been little systematic research on the issue. In our study, we combined data on nearly 750,000 women from the well-established Demographic and Health Surveys with data from the UN Population Division’s World Contraceptive Survey and the Organisation for Economic Co-operation and Development’s Credit Reporting System to examine the policy’s impact on reproductive health issues over a period of 20 years across Sub-Saharan Africa. Our analysis begins when the policy was inactive under Bill Clinton, examining changes when it was then re-introduced by George W. Bush and again rescinded by Barack Obama.

Specifically, we examined changes in contraceptive use, pregnancies, and abortion – and in particular, we isolated changes that vary systematically both with the sharp timing of the policy and with the relative importance of US foreign aid for family planning in each country. A strength of this approach is that it enabled us to separate the policy’s effect from other, confounding influences.

What we find is a stark, quantitative pattern that shows when the policy is in place, contraceptive use decreases by 13.5%, pregnancies increase by 12%, and importantly, abortions increase by 40% in countries most reliant on US funding compared to when the policy is inactive.

Abortion is difficult to measure, much less measure precisely because of the sensitivity surrounding it – and we carefully test different approaches – but the pattern is striking.

While it may at first seem surprising that the Mexico City Policy increases abortions, this pattern of results makes sense. Because many of these organizations are important providers of contraceptives and family planning across Africa, when the policy is active, the supply of these services falls – and the rest of what we find then flows from this: less contraceptive use, more pregnancies, and more abortion. Given that many abortions are performed under unsafe circumstances, our analysis likely underestimates the full harm of the policy.

And, the financial stakes have recently grown: when President Donald Trump reinstated the policy in January 2017, he expanded its scope to effectively include all US bilateral aid (including funding for organizations focused on HIV/AIDS, maternal and child health, malaria, and nutrition). Roughly 7.4 billion dollars per year are subject to the expanded policy requirements.

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Regardless of one’s political leaning or values, an increase in abortion seems to be an unintended consequence of the Mexico City Policy. There may be little agreement on alternatives to the policy, but not increasing abortion on a large scale, even unwittingly, could potentially be a common goal. And the data shows that the Mexico City Policy does not achieve that.