Here’s a paradox: Kerala, a state with sub-replacement level fertility rates, is also home to three of the world’s ten fastest-growing cities by population.

Northern Kerala’s Malappuram is the world’s fastest-growing city, recording a 44% increase in population between 2015 and 2020, according to The Economist based on UN data. The other two Kerala cities that feature in the top 10 are Kozhikode and Kollam.

Source: The Economist via Quartz

Kerala’s cultural capital of Thrissur also features at number 13. Gujarat’s Surat at 27 and Tamil Nadu’s Tiruppur at 30 are the only other Indian cities in the top 30.

Kerala’s decadal fall

These statistics show Kerala is a study in contrasts as far as demography goes. At 4.6%, Kerala had the lowest decadal population growth rate in the country, according to the 2011 census. This is much below the national rate of 17.6%. Bihar had the highest decadal population growth at 28.6%.

“Kerala is moving towards zero population growth or even negative population growth,” according to the state government’s Economic Review 2016. The trend has been generally attributed to the state’s high levels of literacy, especially among women.

The child population – comprising those up to six years old – in Kerala, too, witnessed a negative trend in 2001-’11 at -8.44%. The state’s total child population in 2011 was 3,472,955 compared to 3,793,146 in 2001. The child population represented 10% of Kerala’s total population in 2011, down from 12% in 2001.

However, the low overall population growth in the 2011 census was a result of negative rates in some districts offsetting high rates in other regions. Malappuram’s population, for instance, grew at 13.4% in the decade till 2011. The highest proportion of child population – 14% – was also in Malappuram district.

This article first appeared on Quartz.