THE BIRTH CONTROL REVOLUTION: New analysis of the role of contraception in the demographic transition to low birth and death rates

Demographers have long observed that as a country evolves from a pre-industrial society to an industrialised one, it undergoes a transition from high birth and death rates to lower birth and death rates. Today, countries are at various stages of this demographic transition: the highly developed ones have completed it and most developing countries are well on their way.

New research by Professors Joydeep Bhattacharya and Shankha Chakraborty posits that accompanying these radical changes is a somewhat overlooked contraception revolution in deliberate limitation of family size that is essential for the demographic transition to occur. Their study, which is published in the November 2017 issue of the Economic Journal, explores how that birth control revolution has brought remarkable economic benefits to modern couples.

World population growth has declined rapidly since the 1960s. The average number of children a woman has in her life has fallen by 50%: from 5.0 births in the early 1950s to 2.5 births in 2010. Women in developing countries – with the exception of sub-Saharan Africa – have transitioned from having around six births during their lifetime to having closer to two births.

Sometimes, it is best to look at these sorts of epoch-defining events through a historical lens. Victorian England is a good place to begin since, by many counts, this is where it all started. In Victorian England, life expectancy at birth rose from near 40 by 1830 to 50 by 1900. A newborn during 1861-70 had a 27.9% chance of dying before reaching the age of five; by 1911-20, the chance was only 16.5%. At the same time, marriages in 1860, when they lasted 20 years or more, produced an average of 6.16 births; by 1915, that number had declined to 2.43.

Accompanying these mortality and fertility changes was an underappreciated revolution in family-size limitation – a contraception revolution – whereby a new paradigm of conscious prevention (via natural or artificial means) of unwanted pregnancies subsequent to reaching a family-size target took hold.

There is indirect evidence that this revolution was happening: 32.9% of women born in the period 1840-69 had two or fewer children (live births) ever, compared with 57.5% of women born in the period 1870-99.

The researchers propose a theory where the various facets of the demographic transformations become causally entwined. In their story, one or more factors lower desired fertility of couples, be it rising adult wages that raise the opportunity cost of childbearing or declining child mortality that creates too many surviving children.

In such a scenario, if the natural process of procreation is unrestricted, families would be likely to overshoot whatever family-size target they may have set. If child mortality is high, this may yet keep the number of surviving children close to target. But if child mortality declines precipitously, as it did in England, couples must adopt some method of birth control to stay on target.

Depending on cost considerations – some social (serious opprobrium from clergy and doctors, even for coitus interruptus), others informational – that may mean switching from cheaper, less effective, traditional methods of birth control to costlier but effective and modern ones. Faced with the precipitous decline in child mortality from the 1870s and the possibility of exceeding their target fertility, families found it worthwhile to pay the higher fixed cost and switch to modern, more efficient, methods of contraception.

The initial ''switchers'' were the rich, those unfazed by the higher fixed cost of the modern methods. Eventually everyone switched and the fertility transition was largely completed within three generations. Hastening the switch was the decline in child mortality. Counterfactuals based on the model suggest that in the absence of this contraception revolution, the total fertility rate would have been more than a third higher three generations into the demographic transition.

Although this research is inspired by historical England, it offers several insights into modern demographic transitions currently under way in developing countries. For one, it puts child mortality centre stage: if a country is to spur a birth control revolution, it must devote resources to bring down child mortality.

Second, while access to information regarding effective means of birth control are no longer major stumbling blocks in the lives of modern couples anywhere, family planning, especially a woman''s right to choose her preferred method of birth control, continues to be controversial in many countries.

More broadly, the authors provide a framework in which the competing forces of economic growth, health improvement and social change facilitate demographic change. Rather than one, universally valid source of fertility change, the researchers anticipate that the proximate causes of fertility change have differed across modern societies depending on their socio-economic characteristics.

''Contraception and the Demographic Transition'' by Joydeep Bhattacharya and Shankha Chakraborty is published in the November 2017 issue of the Economic Journal. Joydeep Bhattacharya is at Iowa State University. Shankha Chakraborty is at the University of Oregon.