Chinese megacities like Shanghai need to look beyond outdated policies that limit the population and restrict migration

Rapid population growth in megacities is increasingly a key challenge to urban management. Take Shanghai, for example. The number of permanent residents there stood at 16.4 million in 2000, and had risen to 23 million by 2010. At the end of 2014, that figure had reached 24.3 million.

From 2012 onwards, following the third plenum meeting, policies have been gradually introduced that aim to control populations in China's largest cities. The strategy aims to "systemically relax restrictions on household registration in designated towns and small cities" and "strictly limit the population of megacities".

As a result, how to identify and carry out comprehensive population management in Shanghai is now a heated topic of academic discussion and policy research. Indeed, urban governments have stressed the need to manage their populations.

Following economic reform, and especially after the development of Pudong, increasing investment and rapid economic development have brought many job opportunities and migrants to Shanghai. Urbanisation has also pushed workers out of the countryside, and the central and western region, to eastern coastal cities such as Shanghai. Big cities remain the main target, especially for younger migrants, according to recent census data and surveys.

Migration is one phenomenon that accompanies urbanisation. Investment and industrial development improves employment prospects and provides new opportunities for entrepreneurship. These economic factors cause population growth in cities.

Meanwhile, urban space expands, leading to increased housing provision, which allows migrant numbers to grow. Population control that disregards or violates these intrinsic rules of urbanisation will not only encounter difficulties in achieving the intended effect, but will also even hinder urbanisation per se.

For Shanghai and other mega-cities, the main challenge to limiting its population is that China's urbanisation is on a fast track. The rate of urbanisation has risen from 20 per cent in the 1980s to 54.8 per cent in 2014, accelerating quickly after 2000.

But there are still 670 million people in rural China, and it is estimated that another 200-300 million will migrate to urban areas in the next two decades. Urbanisation causes structural changes to industry and migration. Megacities in coastal areas with greater industrial and economic prowess, which are more able to attract resources, have become hubs swarming with people.

In the 1990s, urbanisation was mainly fuelled by small and medium-sized cities, but metropolises and megacities have increasingly become the major dynamic as their industrial might grows. From 2000 to 2010, cities such as Shanghai, Beijing and Guangzhou had greater industrial and economic opportunities, and so people flocked there. As the most urbanised, they will certainly play a bigger role in attracting migrants.

Some believe that China's industrial transformation away from low-wage, low-profit and labour intensive industries will control urban populations.

Although such a strategy is worth encouraging, the consequences are still not certain. The service economy will require more workers, and the development of the hi-tech industry will see a greater demand for services, and also lead to an expansion of low-end industrial jobs. Furthermore, in any city, the purpose of economic growth is to create employment and produce wealth, not to control the population.

The intrinsic rules of urbanisation and spatial dynamics also determine where populations are centred. Classic urban geography argues that a cluster effect occurs in the early phase of urban development; at the mid- to late stages, the trend is one of urban sprawl to the peripheries. Population concentrations during urbanisation are a result of economies of scale. And when the marginal benefits of urban economies of scale diminish, areas on the periphery will develop into sub-cities, forming a multi-centred metropolis.

Hence, megalopolises like Shanghai are no longer single-centred cities; the beginning of the 21st century has seen the emergence of suburban new towns expanding out to create a multi-centred metropolis. Downtown population numbers have started to fall, and the suburbs and sub-city centres are still seeing a bigger influx of migrants, and actually need immigrants to sustain their growth.

In this sense, strict curbs on megacities' population growth could be regarded as a continuation of the urbanisation strategy of the 1990s, namely, one with a focus on smaller cities and strict control over big cities.

However, as Chinese urbanisation has entered the multicentric, mega-city stage of development with regional urbanisation, leaders must move away from an obsolete urban development strategy.

Rather, other factors need to be taken into account, such as regional variations and how the urban system evolves at different stages. Shanghai and the Yangtze River Delta region should take a holistic view of development. As megacities such as Shanghai evolve into multicentred city complexes, simply limiting the population doesn't necessarily accord with the new realities.

Rather than seeking to control urban population and restrict migration, Shanghai should attach more importance to urban layout to attract new talent, particularly to its service industries, and implement spatial changes to enlarge the city's capacity to ensure prosperous development of this multicentred megalopolis.

Yuan Ren, PhD, is professor of demography and urban studies at Fudan University