By Jennifer Dabbs Sciubba

Most experts agree that the mark of long-term success in Afghanistan will be stable governance that allows the economy, democracy, and the people to flourish. Many factors will determine that, but a major one that seems to be left out of most high-level conversations is population.

Afghanistan is a country of 31 million people, but that number will double by 2035, according to the most recent U.N. projections, and could reach 126 million by midcentury. That's 95 million more Afghans to govern, clothe, feed, and employ.

Without attention to population, countries like Afghanistan and Pakistan stand a good chance of staying mired in poverty, conflict, and corrupt, repressive government. That is why sustained investment in family planning by the United States and other countries would do more to stabilize the political climate there than any other foreign-policy initiative. Though efforts by the Afghan government to provide contraceptives have met some resistance by conservative Muslim groups, the success of family planning in other Muslim states demonstrates that it can be effective.

Over the last 40 years, 80 percent of all outbreaks of civil conflict occurred in countries with a youthful age structure, which creates demands on food, water, and land. And never has this phenomenon been more evident than in the recent conflicts in Egypt, Libya, Yemen, and other nations in the Middle East. Afghanistan's population is far younger than those of even these states. Even if Afghanistan achieves lower fertility, it will not have as old an age structure as either Egypt until after 2045 or Tunisia until 2065. This means decades of instability and turmoil ahead.

Family planning can make a huge difference in a country's long-term fate.

Hosni Mubarak noted in a 2008 speech how Egypt and South Korea each had a population of 26 million in 1960, but today South Korea has 48 million people and Egypt about 80 million. The median age in Egypt is 24 years, and in South Korea it is 38. Egypt is mired in conflict and lacks democracy, while South Korea has stable governance and one of the fastest-growing economies in the world.

Smaller family sizes allow each child to receive a larger share of household resources, and mothers can seek employment outside the home. Education and family planning can reduce abortions, maternal mortality, and infant mortality, and break the cycle of poverty.

We need a comprehensive approach to building national security, one that addresses issues not only with military efficiency and effectiveness, but also with family planning, democratic accountability, poverty reduction, and education. Reproductive health and family planning should be a cornerstone of U.S. and international policy in Afghanistan and the region. Despite the fact that family planning is one of the most effective foreign-assistance programs the U.S. funds, support for it has been declining since 1995.

Our nation and its allies want a more peaceful world in general, and development, peace, and strong governance in Afghanistan, in particular. High population growth rates and a youthful population impede those goals, but sustained attention to family planning can contribute to a successful transition to democracy.