Every minute, dozens of people in East Asia move from the countryside to the city.
The massive population shift is creating some of the world's biggest mega cities, including Tokyo, Shanghai, Jakarta, Seoul and Manila, as well as hundreds of medium-sized and smaller urban areas.
This transformation touches on every aspect of life and livelihoods, from access to clean water to high-speed trains that transport millions of people in and out of cities during rush hour each weekday.
People move to urban areas in search of more jobs and a better life. However, urbanisation comes with risks that can prolong impoverishment and lack of opportunity instead of improving future prospects.
Once cities are built, their urban form and land-use patterns are locked in for generations. Getting it right prevents spending decades and large sums of money trying to undo mistakes.
Therefore, it is important to understand the inter-related mega trends that accompany urban growth. To do so requires monitoring and tracking the complex issues involved, including migration, labour, employment, income, transport, health, education and public infrastructure.
Big data can be a very useful tool in this exercise, which is the focus of our new report titled East Asia's Changing Urban Landscape: Measuring A Decade Of Spatial Growth.
It uses satellite imagery and geospatial mapping of the region's urbanisation in the first decade of the 21st century.
Defining urban areas as those with a population of at least 100,000 inhabitants, this report uses comparable data - on an international scale - to track the expansion of 869 cities and its links with key socio-economic trends.
The report's findings bring a fresh perspective on what is happening:
- Almost 200 million people moved to urban areas in East Asia from 2000 to 2010 - a figure equal to the world's sixth-largest country. It took more than 50 years for the same number to become urbanised in Europe.
- China's Pearl River Delta has overtaken Tokyo to become the largest urban area in the world in terms of both land area and population size. It is now more than twice as large as the Shanghai urban area, four times the size of greater Jakarta and five times the size of metropolitan Manila.
- Economic output per capita increased throughout the region as the percentage of people living in urban areas went up, showing a direct link between urbanisation and income growth.
- Less than 1 per cent of the total territory of East Asia is urbanised (close to the size of Cambodia), and only 36 per cent of the total population is urban - suggesting significant scope for urban growth in decades to come.
- Urban areas in East Asia were 1.5 times as dense as the global average and they are getting slightly denser - from 5,400 people per square kilometre in 2000 to 5,800 per sq km in 2010.
The report also exposes some of the challenges posed by urbanisation in East Asia.
Almost 350 of the East Asian urban areas have expanded across local administrative boundaries, thereby fragmenting their management and revenue sources. In some cases, multiple cities are merging into a single entity while they continue to be administered separately.
While urbanisation in the region is largely driven by market forces, policymakers at the national and municipal levels have an important role to play in ensuring it is sustainable and inclusive.
We are releasing this comparable data so that governments, urban leaders and researchers in East Asia and elsewhere can get a better picture of recent trends and ensure that the unstoppable demographic, social and political transformation of cities helps reduce poverty and boost shared prosperity.
The report offers new ways of looking at where urbanisation has gone wrong and where it is done right so that it works for people.
Some of the best policy approaches include: facilitating access to land and guiding development so it can occur efficiently; ensuring high-density areas are well located and planned to produce a livable and walkable environment; addressing the entire system of cities by coordinating urban services across municipalities and governments; and making urbanisation inclusive so economic opportunities are available, including to recent urban migrants.
This new urbanisation data is a tool to help policymakers and planners build better cities for the millions of people who are moving into East Asia's urban areas in search of a better future with more jobs and opportunities for everyone. It will also be a useful tool for those outside East Asia to also learn from the region's experience.
The writer is World Bank vice-president for East Asia and Pacific.
The report is available at www.worldbank.org/eap/MeasuringUrbanExpansion