BOSTON – It is perhaps inevitable that contraception and population growth are controversial topics, given the many perspectives brought to bear on them. Reproductive-health activists focus on family planning and a woman’s right to control her own body. Economists look at the impact on sustainable growth. Governments fret about over-population and unemployment. Health workers worry about sexually transmitted diseases and malnutrition. Striking the right balance among these different viewpoints is no easy task – but much depends on getting it right.

New contraceptive technologies – in the form of condoms, pills, and implantable devices – provide reversible and permanent forms of protection. But their usage varies widely – from just 4.8% of young women in Chad to 84.6% in China – reflecting differences in cost, availability, and cultural norms.

Contraception indisputably brings health and socioeconomic benefits. A 2012 study reported that its use averted an estimated 272,040 maternal deaths in 2008, 44% fewer than might otherwise have occurred. Contraception use has also helped less developed economies by raising women’s employment and earnings potential.

But perhaps one of the most important economic effects of contraception concerns the "dependency ratio” – the proportion of available workers to pensioners, children, and the infirm. Lowering the birth rate lowers the overall dependency ratio – though at the risk of future labor shortages, weaker consumer spending, and reduced productivity. And, as more people live longer, and the relative size of the working-age population falls, the dependency ratio can begin to rise, with serious socioeconomic repercussions, because older people require more health care and draw pensions.

On the other hand, rapid population growth as a result of higher birth rates can threaten the wellbeing of the poorest communities and countries, by altering the dependency ratio at the other end of the scale. Sub-Saharan Africa and the world’s other poorest regions have recorded significantly more than 2% annual population growth in recent years, whereas the demographic trend in the advanced economies of Europe and Asia has been flat or declining 

Simulations indicate that the optimal average number of children born to a woman over her lifetime is around 2.3. This is the total fertility rate (TFR) required to maintain current population levels (the replacement rate). Unfortunately, few countries strike the right balance, with country averages ranging from 6.9 (in Niger) to 0.8 (in Singapore). The CIA World Factbook reports that 141 countries (approximately half of the world’s population) fall below the replacement rate, with population decline projected in some cases to reach 20% by 2050.

Some countries, such as Germany and France, are trying to raise their TFR to the replacement level. Others are struggling to bring down their TFR, because of fears about future mass unemployment and social unrest. In all cases, economic circumstances and social pressures will dictate the level and speed of population growth.

That is why much attention has focused on the impact of a growing global population on food demand. A rising population has been associated with starvation and malnutrition in some parts of the world. Until recently, the global population was predicted to surpass 11 billion by 2050, triggering Malthusian fears. Thanks in part to lower fertility rates in industrialized countries, this projection has been adjusted downward, to about 8.9 billion.

But such fears remain. The risk is that policymakers and campaigners will conflate the problems of food shortages and starvation with that of population management and its long-term social and economic consequences. In fact, according to a forecast in 2002 by the United Nations Food and Agricultural Organization (FAO), global food production will exceed the needs of the global population by the year 2030, largely owing to the Green Revolution of the past half-century.

Karen Buch is Senior Resident in Radiology at Boston University Medical Center. Duksoo Kim is Professor of Radiology at Boston University School of Medicine, Chief of Vascular and Interventional Radiology at the Boston VA Healthcare System, and Founder of FoodSolutions Without Borders.

Copyright: Project Syndicate, 2014.