Feature: London heading for megacity status by 2026

The population of London has grown by 5.7 percent over the four years to mid-2015, and a city that only a couple of decades ago was in population decline is now set to hit megacity status of 10 million people within the next 11 years.

Figures released Wednesday by the Office for National Statistics (ONS) show that London's population grew from 8.2 million to 8.67 million between mid-2011 and mid-2015.

The ONS report noted that "Greater London stands out" as by far Britain's largest city region and also its fastest growing. Its comparatively young population age structure means it has a higher birth rate and a lower death rate than other areas too.

Births accounted for a 6.4 percent growth in the population, while deaths were a 2.3 percent decline. London's attraction to immigrants also reflects its status as a major employment centre and international hub.

International immigration accounted for a 4.8 percent growth in population.

Against the current economic and political backdrop of Britain's vote to leave the European Union, figures show there is a net outflow of Britons from the city.

The report noted: "Uniquely among the city regions, London has a high net internal inflow of people aged 22 to 29, reflecting its attraction for graduates in particular."

The internal migration flow of this group saw a 2.8 percent increase each year, the only age group of Britons which increased.

In other age groups larger numbers of people move out, the report citing potential reasons including the "high cost of property for people forming a family, plus lifestyle choices," leading to a 3.1 percent decline in population.

REVERSING POPULATION DECLINE

London's gathering population increase is a reversal of a post-Second World War trend.

Some 25 years ago, the population total of London was in a long-term decline. The city had grown hugely and without much planning during the Industrial Revolution and the Victorian era, to become the largest city in the world.

The first British census in 1801 recorded London's population at just over 1 million people. The capital grew at a rate of around 20 percent per decade throughout the 19th century reaching 6.5 million in 1901.

Over the first three decades of the 20th century, the population continued to grow, but at a slower rate up to a peak in 1939 of 8.61 million.

The size of London's population then began a period of decline, initially resulting from the impact of the Second World War and then in later years the result of changes to social structures and increasing urbanization of suburban areas.

By 1950, the population had fallen to 8.1 million, and by 1971 it was at 7.3 million, according to figures from the Greater London Authority.

By 1988, the population of London was 6.7 million, a decrease of around 22 percent since 1939.

The last decade of the 20th century saw London's population begin to rise again, and between 1991 and 2011 the capital increased in size by 1.7 million people.

GROWING TREND OF MEGACITIES

Megacities, those with a population total of over 10 million, are a growing global trend, driven primarily by the increase in urbanization in Africa and Asia, which are still predominantly rural but which are forecast to continue a rapid pace of urbanization to become majority urbanized by 2050.

In 1990, there were 10 megacities, in 2014 there were 28 -- six of them in China -- and by 2030 there will be 40. Current megacities include Beijing, Shanghai, Tokyo, New York, Delhi, and Sao Paolo.

A total of 90 percent of the growth in urbanization over the next 14 years is expected to take place in Asia and Africa, said the UN, with China, India and Nigeria accounting for nearly 40 percent of that growth.

Within the developed world, few citizens live in megacities, although the majority of the population is urbanized.

In 2014, the Department of Economic and Social Affairs of the United Nations issued its Urbanization Prospects report, which showed less than 8 percent of European citizens lived in a megacity, yet 73 percent of the population lived in an urban environment. The rate of urbanization in Europe has declined from about 1 percent increase a year in 1950 to about 0.3 percent now, and is forecast to remain at that level.

London's growth forecast over the next 11 years is unusual in this context, and reflects its status as a capital city, a global financial center, and a global or continental hub for arts, culture, education, travel, and tourism.

The ONS report also noted that the British population reached 65.1 million in mid-2015, an increase over the previous year of 513,300 (up 0.8 percent).

This national increase was driven by net international migration of 335,600 and natural change (births minus deaths) of 171,800. Endit