Special Report

The World’s 33 Megacities

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As of 2009, more than half of the world’s population lived in urban areas. By 2050, the U.N. projects that two out of every three people live in an urban area. This ongoing shift to big cities could fundamentally change the way we think about many critical issues, like disease control. The COVID-19 pandemic has highlighted one of the potential drawbacks of living in a highly dense megacity, defined as having populations greater than 10 million.

People in close proximity are more likely to catch and spread the SARS-CoV-2 virus, which causes COVID-19. Health experts believe New York City has been especially hard-hit by the virus because of its U.S.-leading population density of 28,000 residents per square mile, in addition to the high number of international tourists and its reliance on public transportation. The tourism industry — like others — has grinded to a halt as a result, however. These are the US industries being devastated by the coronavirus.

The susceptibility of these cities to this and other viruses also depends in large part on the response by national and local governments. In early February, China restricted entry to megacities Tianjin, Guangzhou, and Shenzhen. India, home to a number of megacities on this list, instituted a nationwide lockdown in late march. The response to the coronavirus in America has been more fragmented, directed by state and local leaders. Many have shut down non-essential businesses like bars and restaurants. These are the places that have mandated bar and restaurant closings.

To identify the world’s 33 megacities, 24/7 Wall St. used “The World’s Cities in 2018,” the latest edition of the U.N.’s biennial population data booklet. All data on population, population projections, and the percentage of a nation’s population residing in urban areas are from this source.

It is important to note that there are no standard global criteria for determining the boundaries of a city for the purpose of population studies. Some estimates look only at the population inside a city’s administrative boundaries, known as the “city proper” population. Other population measures include surrounding suburban communities that have economic ties to a nearby urban core but can stretch for hundreds of square miles through small farming communities and national parks.

Click here to see the world’s 33 mega cities
Click here to see our detailed findings and methodology

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33. Bangkok, Thailand
> 2018 population: 10.2 million
> 2000-2018 population growth: +58.8%
> Pct. of Thailand’s population: 14.7%
> Est. 2030 population: 12.10 million

Thailand’s capital is one of the most visited tourist destinations in the world. Situated on the Chao Phraya, one of the region’s most important rivers for trade and rice production, Bangkok has historically been an important trading post and is today the country’s urban nerve center.

Though it is known as the Land of Smiles, Thailand has endured sometimes caustic urban-rural divisions, with 80% of the country’s poor living outside the relatively prosperous capital. Even so, Thailand is an oft-cited example of economic development success as the nation has reduced the percentage of those living in poverty over the last four decades.

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32. Lima, Peru
> 2018 population: 10.4 million
> 2000-2018 population growth: +42.5%
> Pct. of Peru’s population: 31.9%
> Est. 2030 population: 12.27 million

Surrounded by a coastal desert, Lima, which is situated on the Pacific Ocean, is Peru’s commercial and political center. Nearly a third of the country’s population resides there. The city, with its modem condos rising above pre-colonial ruins, is the second-most arid world capital after Cairo.

Once a tranquil city, Lima is now a busy metropolis because of rapid economic development and population growth. The country was one of Latin America’s fastest growing economies between 2002 and 2013, according to the World Bank.

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31. Chennai, India
> 2018 population: 10.5 million
> 2000-2018 population growth: +58.6%
> Pct. of India’s population: 0.8%
> Est. 2030 population: 13.81 million

Formerly known as Madras, Chennai is the capital of India’s southernmost state, Tamil Nadu and is the smallest of five megacities in India. From a British trading post established in the 17th century, the city has grown into a bustling urban center with an industrial emphasis on automotive, electronics, and health care. About 45% of the auto parts made in India come from Chennai, earning the city the nickname the “Detroit of Southern Asia.” Chennai is also one of the largest information technology hubs. With hundreds of Hindu temples and several nearby beaches along the Bay of Bengal, Chennai is also one of South India’s most popular domestic and foreign tourism destinations.

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30. Jakarta, Indonesia
> 2018 population: 10.5 million
> 2000-2018 population growth: +25.4%
> Pct. of Indonesia’s population: 3.9%
> Est. 2030 population: 12.69 million

Indonesia’s capital, along with Manila and Bangkok, is one of three megacities in Southeast Asia on this list. Located on the northwest coast of Java (the country’s fourth largest and by far most populous island), Jakarta is the crowded, traffic-snarled, beating heart of this archipelago nation of 269 million people.

Indonesia is Southeast Asia’s largest economy and one of the world’s largest, and many of its non-agricultural economic engines are based in the capital, with automotive, electronics, medical devices, and chemicals among its largest manufacturing industries. Jakarta is the home of two-thirds of Indonesia’s banking and financial sectors. As in many of the world’s megacities, poverty and pollution pose major challenges.

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29. Bogotá, Colombia
> 2018 population: 10.6 million
> 2000-2018 population growth: +67.1%
> Pct. of Colombia’s population: 21.4%
> Est. 2030 population: 12.34 million

Bogotá, located on a high central Andean plateau, is one of the world’s 13 megacities that is also a national capital. The city is also the political, cultural, and financial center of the second most populous South American country after Brazil.

In 2017, the capital’s economy grew by 8%, compared with national economic expansion of 1.8%. The city is a major destination for foreign direct investment in Latin America, with many foreign companies basing their regional operations there. Bogotá‘s street crime remains a concern, and local polls show public skepticism of the justice system. Still, crime in the city has considerably improve d since the mid-’90s.

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28. Paris, France
> 2018 population: 10.9 million
> 2000-2018 population growth: +12.0%
> Pct. of France’s population: 16.7%
> Est. 2030 population: 11.71 million

The City of Light, founded as a fortified settlement on an island in the Seine River about 2,300 years ago, is Western Europe’s only megacity. Paris is one of the most culturally significant cities in Western civilization and is today a major financial, commercial, and tourist center in the European Union. Paris accounts for 15% of the country’s gross domestic product, according to the Cologne Institute for Economic Research. According to Forbes, 29 of the 31 biggest French companies are based in the greater Paris region.

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27. Bangalore, India
> 2018 population: 11.4 million
> 2000-2018 population growth: +105.0%
> Pct. of India’s population: 0.8%
> Est. 2030 population: 16.23 million

This capital city of India’s southern Karnataka state is the country’s information technology hub and one of the fastest growing cities in South Asia. Indians continue to flock to the city’s burgeoning software and IT industries. Nicknamed the “Silicon Valley of India,” Bangalore is an economic powerhouse and, according to one study by management consultant McKinsey, is on track to become the single largest IT cluster in the world by 2020.

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26. Lahore, Pakistan
> 2018 population: 11.7 million
> 2000-2018 population growth: +110.5%
> Pct. of Pakistan’s population: 5.8%
> Est. 2030 population: 16.88 million

Lahore is the smaller of two megacities in Pakistan, the other being Karachi. The capital of Punjab province, on the eastern border with India, Lahore is a historically important city boasting impressive Mughal and colonial-era architecture, which are major tourist attractions. The city’s Shalamar Gardens site is listed as a UNESCO World Heritage Site.

Evidence of early settlement in the area dates back 5,000 years, and documents citing Lahore by name date back to at least the year 982. Today, the city is grappling with the challenges of rapid urbanization in a country experiencing the fastest pace of rural-to-urban migration in South Asia. Population growth more than doubled between 2000 and 2018.

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25. Shenzhen, China
> 2018 population: 11.9 million
> 2000-2018 population growth: +81.8%
> Pct. of China’s population: 0.8%
> Est. 2030 population: 14.54 million

Shenzhen is the smallest of the six Chinese megacities. Over the past 40 years, the city has turned from a small South China Sea port city of 30,000 into an economic colossus. Shenzhen’s economy is powered by shipping and logistics, high technology, and financial services, and the city is one of the busiest container ports in the world.

This growth occurred after the People’s Republic of China opened the doors to foreign investment in 1980 in several “special economic zones” along its extensive coast. The city has been called the “Silicon Valley of China,” and it attracts a heavy flow of tourists (mostly from Hong Kong, which it borders) drawn to the cheap electronics and other locally manufactured consumer goods.

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24. Moscow, Russian Federation
> 2018 population: 12.4 million
> 2000-2018 population growth: +24.0%
> Pct. of Russian Federation’s population: 8.6%
> Est. 2030 population: 12.80 million

As Paris is the only megacity in Western Europe, Moscow is the only megacity in Eastern Europe. The capital of the Russian Federation was first mentioned in historical documents in the middle 12th century and has since played a key role in Russian history.

Moscow has been Russia’s political, educational, scientific, and industrial heart since at least the time of the Russian Empire in the 18th century. For the past six centuries, the city has also been the spiritual center of the Russian Orthodox Church. In many countries, power and economic clout are centralized in the capital, and this is certainly the case for Moscow as well.

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23. Los Angeles-Long Beach-Santa Ana, United States of America
> 2018 population: 12.5 million
> 2000-2018 population growth: +5.6%
> Pct. of United States of America’s population: 3.8%
> Est. 2030 population: 13.21 million

The Los Angeles metro area is one of two U.S. megacities on this list, though it is considerably less populous than the New York City metro area. Like the Big Apple, the City of Angels is a major U.S. economic hub. It’s not just the main home of the country’s entertainment industry, but also hosts one of the world’s largest port complexes (the ports of Long Beach and Los Angeles). Los Angeles is also a major tourism destination, drawing a record 50 million visitors in 2018.

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22. Guangzhou, China
> 2018 population: 12.6 million
> 2000-2018 population growth: +61.8%
> Pct. of China’s population: 0.9%
> Est. 2030 population: 16.02 million

This provincial capital of Guangzhou is located in the industrial, densely populated Pearl River Delta near Hong Kong. Because of their proximity to each other, the nine big mainland cities of this region (including Shenzhen, another Chinese megacity on this list) are considered by the World Bank to be the world’s largest urban cluster.

Guangzhou has been one of China’s commercial and trading centers for centuries and was the first port regularly visited by European traders, who called it Canton. Guangzhou is one of the four port cities in the Pearl River Delta that together comprise the third largest port in the world after Shanghai and Singapore.

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21. Kinshasa, Democratic Republic of the Congo
> 2018 population: 13.2 million
> 2000-2018 population growth: +114.5%
> Pct. of Democratic Republic of the Congo’s population: 15.7%
> Est. 2030 population: 21.91 million

The African continent has three megacities: Lagos, Cairo, and Kinshasa. The capital of the Democratic Republic of Congo spreads out from the banks of the Congo River and is surrounded by farmed savanna. The city is one of sub-Saharan Africa’s industrial and commercial hubs, with industries largely focused on consumer goods like beer and textiles.

The nation rebounded from a recession in 2018 thanks to stronger worldwide demand for its copper and cobalt. Despite improvements in the sub-Saharan Africa’s economy, poverty and hunger remain critical challenges among Kinshasa city dwellers. The rapid influx of rural residents into the city is also putting pressure on infrastructure, especially in transportation.

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20. Tianjin, China
> 2018 population: 13.2 million
> 2000-2018 population growth: +89.1%
> Pct. of China’s population: 0.9%
> Est. 2030 population: 15.75 million

This northern Chinese megacity is located on a heavily industrialized inlet of the Yellow Sea. It has long been a vital transport and trading center due to its role as the gateway to the country’s capital, Beijing, about 75 miles to the northwest.

Tianjin is so vital to China that it is one of the country’s four municipalities that fall under direct control of the central government. (The other three are Beijing, Chongqing, and Shanghai.) Owing to its rich cosmopolitan history, Tianjin features numerous historical attractions, but like other Chinese urban centers it struggles with air pollution and trade-related congestion. The city has been very aggressive in trying to attract foreign investment and upgrade its infrastructure.

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19. Rio de Janeiro, Brazil
> 2018 population: 13.3 million
> 2000-2018 population growth: +17.6%
> Pct. of Brazil’s population: 6.3%
> Est. 2030 population: 14.41 million

The scenic coastal city known for its beautiful beaches and crowded slums is the smaller of Brazil’s two megacities and one of six megacities in Latin America. Rio accounts for 11% of Brazil’s GDP, with key industries including finance, mining, health care, retail, the production of sugar cane, and, of course, tourism.

A steady influx of migrants from rural Brazil continues to feed the parts of the city that receive little or no services from the state. Some of these camps evolved into shanty towns, known as favelas, on the edges of the city.

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18. Lagos, Nigeria
> 2018 population: 13.5 million
> 2000-2018 population growth: +84.9%
> Pct. of Nigeria’s population: 6.9%
> Est. 2030 population: 20.60 million

Lagos, in southwestern Nigeria, is one of Africa’s three megacities on this list. The city has rapidly become a center of regional commerce, finance, and cargo transport. Spurred by security concerns, the Nigerian government moved the capital from Lagos to the centrally located planned city of Abuja in 1991, but this did not stop Lagos from becoming the hub of Africa’s largest economy. Lagos alone makes up well over half of Nigeria’s industrial and commercial activity, boosted by investment in infrastructure as the city tries to ease congestion.

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17. Manila, Philippines
> 2018 population: 13.5 million
> 2000-2018 population growth: +35.4%
> Pct. of Philippines’ population: 12.7%
> Est. 2030 population: 16.84 million

The capital of the Philippines is the largest of the three Southeast Asian megacities (the other two are Jakarta and Bangkok), and it is the nation’s economic, political, and cultural center. The sprawling coastal metropolis is located on Luzon, the country’s largest island. The city is the country’s manufacturing, transport, and financial center.

Manila produces chemicals, textiles, and shoes, among other products. Metro Manila — which includes the city proper and the surrounding metropolitan area — suffers from problems familiar to other big cities in developing countries, including air pollution, traffic congestion, street crime, and urban poverty In 2020, city officials broke ground on the country’s first subway system.

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16. Kolkata (formerly Calcutta), India
> 2018 population: 14.7 million
> 2000-2018 population growth: +12.1%
> Pct. of India’s population: 1.1%
> Est. 2030 population: 17.58 million

The capital of India’s West Bengal state is the one of five megacities in India and the country’s third most populous behind Delhi and Mumbai. Located on the banks of the Hugli River about 100 miles from the Bay of Bengal, Kolkata is a historic transit point and the main urban center of eastern India.

Originally known for its tea production, Kolkata’s economy includes sectors such as textiles, information technology, production of leather goods, and agriculture. As in other rapidly urbanizing parts of the developing world, Kolkata faces immense challenges in fixing traffic congestion, housing, and urban poverty. One of the city’s biggest problems is urban sprawl, which outpaces the local government’s ability to provide basic services and infrastructure.

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15. Istanbul, Turkey
> 2018 population: 14.8 million
> 2000-2018 population growth: +68.7%
> Pct. of Turkey’s population: 18.0%
> Est. 2030 population: 17.12 million

Over more than 2,500 years, Istanbul has grown from an ancient Greek colony (Byzantium) into the largest metropolitan area in the region that bridges Europe and Asia. For much of that history, Istanbul has been one of the most coveted cities in the world due to its location straddling the global trade chokepoint of the Bosporus Strait.

Today, about 54% of Turkey’s imports and 47% of its exports pass through the city. Istanbul, located about 220 miles from Turkey’s capital, Ankara, is the economic and cultural center of the country. In addition to being a popular tourist destination, the city accounts for nearly 40% of the country’s GDP, while employing over a third of the country’s industrial labor force.

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14. Chongqing, China
> 2018 population: 14.8 million
> 2000-2018 population growth: +88.7%
> Pct. of China’s population: 1.0%
> Est. 2030 population: 19.65 million

Located on the banks of the upper Yangtze River in central China, Chongqing is the country’s only megacity on this list that is not located close to a coastline. Owing to its significance as a center of development for western China, the city is one of the country’s four municipalities that fall under direct control of the central government. Some architectural remnants of the city’s past survived, today shadowed by a modern city skyline..

The city’s GDP was $295 billion in 2018, powered by its robust manufacturing base and aggressive state investment in infrastructure. The city, known as the gateway to the scenic Three Gorges river valleys, boasts numerous tourist attractions. The World Travel & Tourism Council named Chongqing in 2016 as the world’s fastest-growing tourism city.

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13. Buenos Aires, Argentina
> 2018 population: 15.0 million
> 2000-2018 population growth: +19.7%
> Pct. of Argentina’s population: 33.5%
> Est. 2030 population: 16.46 million

The Argentine capital is one of Latin America’s six megacities and the third largest urban area in the Western Hemisphere after Mexico City and São Paulo. It is also home to the largest port in South America, the result of the country’s heavy reliance on the production and export of agricultural commodities. Local industries include banking, automotive assembly, oil refining, beverages, and chemicals.

The city is gradually shifting to a more service and technology-focused economy and away from a reliance on industry. Tourism is a major driver of the city’s economic activity, and the capital is the most visited city in South America.

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12. Karachi, Pakistan
> 2018 population: 15.4 million
> 2000-2018 population growth: +56.7%
> Pct. of Pakistan’s population: 7.7%
> Est. 2030 population: 20.43 million

Karachi is the larger of Pakistan’s two megacities, serving as both the country’s primary seaport and its commercial and industrial center. Decades of urbanization have turned this once relatively sleepy port town into a busy metropolis ringed by urban sprawl. Major industries in the city include finance, textiles, pharmaceuticals, steel, and automotive assembly. Karachi accounts for about 25% of Pakistan’s GDP.

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11. New York-Newark, United States of America
> 2018 population: 18.8 million
> 2000-2018 population growth: +5.6%
> Pct. of United States of America’s population: 5.8%
> Est. 2030 population: 19.96 million

The New York-Newark metropolitan area is the larger of the two U.S. megacities (the other one being Los Angeles-Long Beach-Santa Ana) and one of the country’s major economic, financial, and cultural centers. New York City became the country’s most populous urban areas in the early 1800s and has remained the country’s largest ever since. Major local industries include financial services, health care, real estate, retail, education, and media. In 2017, New York City was the sixth most visited city in the world.

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10. Osaka, Japan
> 2018 population: 19.3 million
> 2000-2018 population growth: +3.3%
> Pct. of Japan’s population: 15.2%
> Est. 2030 population: 18.66 million

Osaka, the smaller of two Japanese megacities, is significantly smaller than the world’s most populous city — Japan’s capital, Tokyo. Located in south-central Japan, Osaka is a bustling but orderly port city that’s part of an industrial zone that includes neighboring Kobe and Kyoto. Once a textile town, Osaka’s economy is largely based on heavy industry, including metal fabrication, chemicals, and food processing. Osaka is also widely considered to be a city for foodies with a reputation as having the best culinary scene in Japan.

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9. Dhaka, Bangladesh
> 2018 population: 19.6 million
> 2000-2018 population growth: +90.4%
> Pct. of Bangladesh’s population: 11.8%
> Est. 2030 population: 28.08 million

The centrally located river-port capital of Bangladesh is the economic, political, and educational heart of the world’s eighth most populous country. It is also the country’s most densely populated city.

A major source of jobs is the garment industry, which has been the focus of workplace safety issues following the 2013 collapse of the Rana Plaza building that killed more than 1,100 garment workers. Even by megacity standards, Dhaka is a crowded place. In 2012, urban policy analyst Wendell Cox estimated that the city’s population is denser than 23 other megacities, including Mumbai and Karachi, and that the densest part of Manhattan is 40% less dense.

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8. Beijing, China
> 2018 population: 19.6 million
> 2000-2018 population growth: +90.7%
> Pct. of China’s population: 1.4%
> Est. 2030 population: 24.28 million

In China’s most densely urbanized regions, such as the southern Pearl River Delta, it can be difficult to know where one big city ends and another begins. The country’s capital may be China’s second largest megacity, after Shanghai, but its proximity to other large cities, including the megacity of Tianjin 75 miles to the southeast, makes Beijing the core of a sprawling industrialized, traffic-choked, and heavily populated urban cluster.

Introduction of free-market reforms in the 1990s have led to foreign investment, contributing to the city’s growth. The city’s economy includes the machinery, textile, agricultural, and petrochemical sectors. Beijing has been the seat of Chinese power for more than 800 years, making it one of the oldest (and certainly the most populated) political headquarters in the world.

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7. Mumbai, India
> 2018 population: 20.0 million
> 2000-2018 population growth: +23.7%
> Pct. of India’s population: 1.5%
> Est. 2030 population: 24.57 million

The island capital of India’s south-central Maharashtra state is the country’s main financial and commercial hub and is home to the country’s vibrant native film industry. Historically, Mumbai was the center of the country’s cotton textile industry, but today the city has developed a more diverse economy, including a growing information technology sector, automobile manufacturing, food processing, and petrochemicals.

Constrained by its geography (it is spread over seven islands), Mumbai struggles to provide adequate housing and opportunities for the ever-growing population of rural poor arriving in the city. After the worst flooding in a decade, experts in 2017 called on local officials to do more to control urban sprawl.

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6. Cairo, Egypt
> 2018 population: 20.1 million
> 2000-2018 population growth: +47.3%
> Pct. of Egypt’s population: 20.2%
> Est. 2030 population: 25.52 million

The largest of Africa’s three megacities has roots going back to the ancient city of Memphis, founded 4,000 years ago 14 miles southwest of Cairo. Egypt’s capital, situated 140 miles from the Mediterranean coast, was established about 1,100 years ago. The city’s economy is largely dependent on agriculture, petroleum, mining, and, most important, tourism — an industry that was pummeled in the wake of the January 2011 Arab Spring. The tourism industry has recently started to recover, though the number of foreign visitors remains below its all-time high in 2010. Two-thirds of Egypt’s GDP is generated in the greater Cairo metropolitan region.

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5. Mexico City, Mexico
> 2018 population: 21.6 million
> 2000-2018 population growth: +16.9%
> Pct. of Mexico’s population: 16.5%
> Est. 2030 population: 24.11 million

Mexico City is North America’s largest metropolis and the second largest of Latin America’s six megacities, barely trailing behind São Paulo. Located on an ancient lakebed in a high valley ringed by mountains, Mexico City is the economic, political, and cultural center of the country.

The city’s pre-Columbian and colonial sights, as well as its cosmopolitan atmosphere and culinary treats, make it a popular destination for foreign visitors as Mexico is one of the most visited countries in the world. In addition to being a tourist destination, the metropolitan area accounts for nearly 22% of the country’s GDP.

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4. São Paulo, Brazil
> 2018 population: 21.7 million
> 2000-2018 population growth: +27.2%
> Pct. of Brazil’s population: 10.3%
> Est. 2030 population: 23.82 million

The larger of Brazil’s two megacities and the most populous city in the Western Hemisphere, São Paulo is a leading Latin American commercial and industrial center, responsible for about 12% of the GDP of one of the largest economies in the world.

The city has been shifting from an industrial-based economy to one focused on consumer services and technology. Located on a plateau about 36 miles from the Atlantic coast, São Paulo is notable for its dense urban skyline of glass-and-concrete high rises looming over street-level nightclubs and trendy restaurants.

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3. Shanghai, China
> 2018 population: 25.6 million
> 2000-2018 population growth: +79.6%
> Pct. of China’s population: 1.8%
> Est. 2030 population: 32.87 million

Shanghai is China’s largest city by population, and the third-most populated in both Asia and the world as a whole. Located on the central east coast of the country at the mouth of the Yangtze River, the city is home to the world’s busiest port complex in terms of cargo tonnage. In 2017, Shanghai became the first Chinese city with a GDP over 3 trillion yuan ($469 billion in 2017 dollars). The city is also the location of one China’s two stock exchanges.

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2. Delhi, India
> 2018 population: 28.5 million
> 2000-2018 population growth: +81.7%
> Pct. of India’s population: 2.1%
> Est. 2030 population: 38.94 million

Sitting on the banks of a Ganges River tributary in north-central India, Delhi is the largest of the country’s five megacities and also the political center of the country. It comprises Old Delhi in the north, a historic city known for its opulent 17th-century Mughal historical sites, and New Delhi, built in the early 20th century as the seat of the British occupation.

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1. Tokyo, Japan
> 2018 population: 37.5 million
> 2000-2018 population growth: +8.8%
> Pct. of Japan’s population: 29.5%
> Est. 2030 population: 36.57 million

Tokyo has been the reigning champion of the world’s megacities for decades. The industrial and political center of the world’s third largest economy has nearly the population of California crammed into a space smaller than the size of Connecticut. But its days as human history’s largest urban agglomeration are numbered as Japan’s population is projected to shrink, while Delhi’s population continues to expand. The United Nations predicts that by 2029, India’s capital territory will overtake Tokyo as the biggest megacity in the world.

Detailed Findings & Methodology

The population of New York City proper, for example, is 8.4 million, according to the latest U.S. Census Bureau data from 2018. However, the population of the city’s broader area, also known as the metropolitan statistical area, is just under 20 million. The metro area stretches from the tip of Long Island to Allentown, Pennsylvania (191 miles to the west), and from Tuckerton, New Jersey, to Kingston, New York, a 160-mile drive to the north.

In many cases, there is a third category, called the urban agglomeration, which is defined by the U.N. as the contiguous built-up area with urban density that stretches beyond the city boundaries across administrative zones over county and state lines. A suburb located in a neighboring state that is close enough for residents to commute to and from a city would not be considered part of the urban agglomeration but would often be considered part of a city’s metropolitan area.

Based on the U.N. data, only two cities in the Western Hemisphere rank among the world’s 10 most populous cities: Mexico City, with its metropolitan area population size of 21.6 million and São Paulo, with a population size of 21.7 million. Seven of the top 10 megacities are in Asia, while Cairo is on the list at No. 6 with 20.1 million.

In order to maintain an apples-to-apples comparison of city population sizes, we are relying solely on U.N. estimates. The number of megacities — defined as cities with populations greater than 10 million — grew from 28 in 2014 to 33 in 2018, more than triple the number in 1990.

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