Bengaluru: Three Indian cities were listed among the 10 fastest-growing cities globally, in a ranking released by The Economist on January 7, 2020. This was widely shared and discussed on social media as all the three cities--Malappuram, Kozhikode and Kollam--are in Kerala and have never featured in public imagination as rapidly-growing urban metropolises. Part of the debate took on communal overtones as Malappuram lies in a Muslim-majority area. Others attributed this growth to the recent wave of labour migration from North India into Kerala.

A worldwide comparison of the growth of cities based on the single parameter of population may be too simplistic and misleading, an analysis of the methodology and a comparison with Census data, by the Urban Informatics Lab at the Indian Institute for Human Settlements, Bengaluru, found.

The Economist ranking was prepared using data from the UN Population Division, which states that the definition of ‘urban agglomeration’ and the classification of urban and rural areas vary significantly across countries. This limits a global comparison of urban growth.

The UN data also assume a nearly linear trend to calculate the growth of Indian cities from 2015 to 2020, based on the 2011 Census of India. For Kerala’s cities, this may not be accurate because a large fraction of rural areas have already been classified as urban. For instance, two-thirds of the population in Kozhikode district was identified as urban in the 2011 Census. Therefore, subsequent growth would taper off.

Moreover, this ranking was based on a single metric--of population growth--and does not cover the scope of urban development. While population trends, density and non-agricultural workforce are useful indicators for understanding the expansion of urban areas, the presence of basic infrastructure vital for a better quality of life in urban areas--such as water supply, waste management, sewerage networks--needs to be factored in. This ranking does not account for these characteristics.

In the context of Kerala, where the population density does not differ too much across the geography of the state, it is these factors that can better differentiate between urban and rural areas.

What does the chart show?

This chart shows urban agglomerations with a population of 1 million or more as of 2015, listed in terms of the projected growth of their population during 2015-20. The term ‘urban agglomeration’ (UA) refers to a cluster of urbanised areas that are situated so close to each other that they could be treated as a single city for most practical purposes. Often, a UA includes multiple administrative units.

The chart was prepared, as we said, using data from the United Nations Population Division. Population data were gathered from all over the world and projections made for the years for which no data were available, as described in this UN working paper. The UA-level population numbers for India were derived from the Census of India datasets.

Below are charts made using the UN Population Division data that illustrate the population growth of urban agglomerations around the world.

Source: UN Population Division

These charts show the world’s fastest growing UAs, first listing all the UAs (left) and then depicting only those with a population of at least 1 million in 2015. The large-UA chart (on the right) is very similar to the rankings published by The Economist, with some minor differences in the decimal digits.

There are faster growing UAs compared to Malappuram (which ranks 13th if all UAs are considered), but they were not considered for The Economist’s rankings because they did not meet the population threshold of 1 million.

Now, we examine the rankings of only Indian UAs.

Source: UN Population Division

The above charts show that Hosur is the UA in India that experienced the fastest growth. However, if only cities with a population of 1 million and above are considered, Hosur and other smaller cities get excluded.

For many cities, the five-year growth projection for 2015-20 is roughly equal to half the 2000-10 decadal growth, according to projections by the UN, indicating that the method effectively assumes that more or less the same pace of urbanisation will continue in the short term.

Growth of UAs in Kerala

To put things in perspective, we analysed Census data to explain characteristics of some Indian UAs, particularly the ones in Kerala that appear in The Economist analysis.

These charts capture the growth in area (in sq km) and population of Malappuram, Kozhikode and Kollam, and compare them against some of the larger UAs in India. A pattern that stands out is that the Kerala UAs had a sudden increase in area and became comparable to large cities such as Bengaluru and Chennai in size. However, as the chart (on the right) comparing the population growth shows, these Kerala UAs have significantly lower population compared to the large cities. This is because the 2011 Census, represented by the last point on each line, recognised significantly more towns and outgrowths as urban, and included many of those in the nearest UA.

Although the natural growth in population and increase in population density played a role in more areas getting classified as urban, the most important factor in Kerala was the fast decline in agricultural employment in and around the existing urban centres. As the following figure shows, a major part of this change happened during the 1990s, and the 2011 Census, in fact, did a catch-up job in reclassifying several villages as towns.

Comparison to the district population

Since the boundaries of UAs have undergone large changes over time, we could get a better picture of the population growth of different regions if we compare the change in district populations. Malappuram, Kozhikode, and Kollam UAs cover almost all the urban areas in their respective districts. We would expect any significant urban growth in the large UAs to be reflected in the population of the corresponding district. The below graph shows the population growth in the three UAs along with the corresponding districts. While Malappuram district is seeing a steady increase in its population, Kozhikode district has had a moderate increase and in Kollam, the growth has started tapering off.

(Sooraj is a consultant with the Urban Informatics Lab at IIHS.)

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