Jakarta is smaller than it should be

Robert Kelly, Jakarta

By some measures, Jakarta is the fourth-largest city in the world. Traffic congestion, air pollution, over-crowding, crime and rising property prices all attest to its rapid growth, and all are problems the capital's residents have to confront daily.

So it might surprise you to learn that Jakarta is actually too small -- 4.3 million people too small.

The source of this uncomfortable revelation is a phenomenon called Zipf's Law. It states that the largest city in a country tends to be twice as large as the second-largest city, three times larger than the third-largest city, four times larger than the fourth-largest city, and so on.

Zipf's Law is very common, and is found in countries as diverse as the United States, Argentina, Pakistan and Japan. Where the Law doesn't hold, it's usually because the capital city is larger than expected: Notable instances include London, Paris and Mexico City.

All of which makes Jakarta highly unusual -- for Jakarta is actually smaller than Zipf's Law predicts.

Jakarta contains over 9.4 million people. According to Zipf's Law, it should be double the size of Bandung, five times larger than Surabaya, nine times larger than Medan, twenty times larger than Samarinda. In fact, it falls short in every single case. Compared with Medan, for example, Jakarta is barely half the size it should be.

If Java is taken as the reference point, rather than the whole of Indonesia, the same pattern emerges. Jakarta is four times larger than Semarang when it should be six times bigger. It should be eleven times larger than Tegal, yet is only five times the size.

Of course, it is possible that Indonesia is unique in some way: That Zipf's Law doesn't apply and that Jakarta is not "too small". However, this seems unlikely when one considers the diversity of countries where the Law does apply: Why should it apply to the U.S. and Pakistan and not to Indonesia?

It is also possible that Zipf's Law is unimportant, a statistical oddity that countries can safely ignore. Unfortunately, the latest academic research suggests that there are good reasons why urban systems tend to evolve towards Zipf's Law. It appears that Zipf's Law represents an "efficient" configuration of cities, in the sense of maximizing a nation's economic output subject to demographic and transport constraints.

In fact, in all likelihood Indonesia is merely in a state of transition, moving towards Zipf's Law but not quite there yet. If that is the case, Jakarta can expect plenty more growth to come.

To properly conform to Zipf's Law, Jakarta would have to grow by a staggering 46 percent -- roughly 4.3 million more people packed within the city limits! And that assumes that other cities remain at their current sizes. If they themselves continue to grow, Jakarta's population would have to grow yet more to compensate.

Clearly, over the next few years Jakarta's growth is likely to be influenced by a host of other factors, not least the performance of the national economy and government policy towards regional development.

Nonetheless, Zipf's Law does give pause for thought. Next time you find yourself stuck in one of Jakarta's endless traffic jams, console yourself with the knowledge that Jakarta is actually less crowded than it should be.

The writer is a freelance British journalist living in Jakarta. and can be reached at robert_em_kelly@yahoo.co.uk