An estimated ten  to fourteen  million girls - females aged under eighteen - are newly married each year. This affects one in three girls in the developing world . Rates are increasing. According to United Nations estimates, by 2021 there will be over fifteen million newly married girls each year .
This is a problem because child marriage is central to the cycle of poverty and a leading impediment to achieving six out of eight Millennium Development Goals . It is a significant cause of shortened education for girls, which in turn causes diminished welfare for her future children, lower economic productivity and political activity, and possibly higher rates of HIV transmission. Child marriage also leads to higher rates of child mortality, fertility and maternal mortality. It further leads to higher rates of domestic and sexual violence.
Child marriage is clearly complex, but we can understand the two main causes in terms of economics and culture.
Low-income families see child marriage as offering financial security for their daughter . It also reduces the family’s expenses, and may even provide them with an income if the girl is purchased . Girls from poor families are nearly twice as likely to marry before they are women than girls from wealthy families .
But child marriage is also rooted in culture. Religious tradition and tribal expressions may support it . Studies also suggest widespread beliefs that girls can be better shaped into dutiful wives . Bangladeshi parents report acting out of duty , despite reasonably common knowledge of child marriage’s bad effects .
Education - A twenty-nine country study on the effects of child marriage on education found that "[a] woman's age at first marriage is positively related to her total years of schooling; in all 29 countries, women who married when they were 18 or older had more education than those who married at a younger age" .
Child mortality - By abruptly ending a girl’s education, child marriage increases child mortality rates. A cross-national study showed that "in 9 countries the highest rates [of child mortality] occurred among mothers with no education" . The mother’s education was the strongest explanatory variable.
Fertility - A further major cross-national study estimated the impact of education on fertility, estimating that "doubling female secondary school enrollment (from 19 to 38 percent) in 1975 would have reduced the total fertility rate in 1985 from 5.3 to 3.9” .
Maternal mortality - Education also makes girls "considerably less likely to die in childbirth and thereby orphan their children with deleterious consequences" .
Child welfare - A comparative study of survey data from seventeen countries found strong evidence of women’s education positively affecting child health .
Economic productivity - A World Bank paper attempted to measure the potential economic gains of keeping girls in school. It found that "investing in girls so that they would complete the next level of education would lead to lifetime earnings of today's cohort of girls that is equivalent to up to 68 percent of annual gross domestic product" .
Political activity - By ending education, child marriage also prevents women from becoming active community members. Educated women are far better at staffing "their basic health facilities with nurses and their primary schools with local teachers—two vitally important professions that increasingly rely on women" . Furthermore, in India "the quality of health services improved as women’s education levels increased thanks to women’s informed demand and the pressure they put on local services" .
HIV - The evidence is mixed, but it is possible that child marriage also causes higher rates of HIV transmission .
Domestic and sexual violence - There is also good evidence that child brides experience more domestic and sexual violence .
Examples of promising programs that aim to prevent child marriage include:
Empowering girls with information, skills and support networks to enable self-advocacy  - An Ethiopian program called Berhane Hewan did this, and participants were nearly three times more likely to be in school than non-program participants, and were 90 percent less likely to be married .
Providing economic support and incentives to girls and their families - This helps to keep girls in education rather than them marrying early. The Zomba Cash Transfer tried this approach, and participants were 40 percent less likely to marry after one year than girls in the control group . This intervention is particularly interesting because it is simple and scalable.
It is extremely difficult to calculate the effectiveness of child marriage interventions. This is both because of a lack of information about their cost and a lack of rigorous evidence about their success rates. It is also difficult to quantify all the varied, disparate but significant effects that child marriage has.
This is supported by an ICRW report, which argues that "researchers increasingly acknowledge that interventions aiming for community-based social change are not ideally suited for traditional randomized methodology. In the realm of child marriage prevention, more creative evaluation approaches may be necessary to effectively understand and appreciate the extent to which the desirable change has materialized" .
Giving What We Can is thus not currently in a position to establish how cost-effective child marriage prevention is.
Giving What We Can has been unable to identify any promising charities that work on child marriage. One reason for this is that child marriage is worked on primarily by private foundations such as Nike and Ford, and states like India.
Most prominent is the Global Giving Foundation, which manages donations to The Girl Effect Fund, which in turn funds twelve different projects. These projects empower girls with information and skills to enable self-advocacy. In this respect they resemble the successful Berhane Hewan program. However, none of the projects involve the conditional cash transfers which were found to be promising. It is also unclear how transparent the programs are, whether they track their effectiveness and whether they do more than only indicate how donations could be spent.
For this reason, and until we have a better understanding of the cost-effectiveness of child marriage interventions in comparison to other causes, Giving What We Can is not currently recommending charities in this area.
Our full report on child marriage is available here.
Last updated: July 2014