India is on course to becoming the world’s most populous country by 2050, with 1.6 billion people, up from 1.2 billion in 2011. If the country has to curb its population growth, a higher survival rate of its children is important, an IndiaSpend analysis of government data indicates.

In other words, when more children survive, women tend to have fewer children, which increases the survival rates of those children (see table below). In some states, however, where that correlation is not apparent, it has been found that female literacy levels correlate with having fewer children and higher survival rates for those children.

In a span of 42 years, between 1971 to 2013, there has been a 55% reduction in India’s total fertility rate – the average number of children born to a woman of child-bearing age – from 5.2 in 1971 to 2.3 in 2013, according to family and health statistics 2015 released by the Ministry of Health. This reduction is influenced by the decline in India's infant mortality rate – the number of babies who die before their first birthday for every 1,000 live births – from 129 in 1971 to 40 in 2013.

The national population policy of 2000 aimed to reduce the total fertility rate to 2.1 by 2010. While that target has not been achieved, the falling infant mortality has been a leading cause for the decline in fertility rate in India.

A lower fertility rate tends to cause further decline in mortality rates, as families can devote more resources to each child, according to a 2011 study by Harvard University.

The mortality rate of babies tends to be higher in states with a higher total fertility rate, an analysis of government data reveals.

Bihar has India’s highest fertility rate of 3.4 babies per woman, against the national average of 2.3. The state, India’s poorest in terms of per-capita income, has an infant mortality rate of 42, worse than the national average of 40.

States with low female literacy rates have high fertility rates, such as Rajasthan and Bihar, which has India’s highest total fertility rate – 3.4 – and India’s lowest female literacy rate, 50.7%.

Tamil Nadu has a low infant mortality rate of 21 and a total fertility rate of 1.7, which is below the replacement rate of 2.1, the level required to keep the population stable. The fertility rate in 10 Indian states has now fallen below the replacement level of 2.1.

However, in states with low fertility rates, the correlation with infant mortality rate is not entirely apparent. States with low fertility rates – such as West Bengal, Himachal Pradesh and Punjab – are not among the top five states with low infant mortality.

This shows that infant mortality may be one among a few factors impacting fertility. Other factors that affect fertility rates are education, availability of health services and access to and awareness of birth control.

IndiaSpend further compared fertility and infant mortality rates with female education levels and found a correlation. Almost all states with low fertility rates have high female literacy rates. For instance, Tamil Nadu has India’s second-highest female literacy – 89.8% of women are educated, and the country’s second lowest total fertility rate, at 1.7

Literacy in women is correlated with late marriage and better access to contraception, thus stabilising population. Educated women have better social standing and ensure better nutrition and immunisation, improving child health and survival, according to this 2000 study from the London School of Economics by Jean Dreze.

This article first appeared on IndiaSpend, a data-driven and public-interest journalism non-profit.