Creative RF / Getty Images Seoul, Korea is the happiest city in the world because it is wealthy, healthy, relatively crime-free, and looks after its citizens.

That is according to a new report by design and consultancy firm Arcadis, which assesses and then ranks 100 major cities in the world across a few indexes.

In its "people sub-index" it assesses:

Income inequality

Crime

Education

Work-life balance

Health

Affordability

Arcadis found that the Korean government's focus on excellent health and education helped propel Seoul to the number one spot.

"The [government's] program also includes urban planning policies to strengthen the city’s identity, global competitiveness, development direction and innovation in the living environment for citizens," says Arcadis in the report.

"It has 139 projects in 13 districts that plan to transform the urban metropolis into a “safe, warm, dreaming, breathing city”. Seoul’s leaders have taken serious steps towards city sustainability with projects like the Cheonggyecheon urban renewal and river restoration project. This previously polluted area has been transformed into a public recreation space in the heart of the city.

"Restoration not only spurred economic development but also provided much-needed flood protection for the downtown area, boosting Seoul’s economic, environmental and social sustainability."

In 2013, government officials launched the Seoul 2030 Plan which is aimed at promoting the following:

"A people-centered city without discrimination."

"A dynamic global city with a strong job market."

"A vibrant cultural and historic city."

"A lively and safe city."

"Stable housing and easy transportation, a community-oriented city."

Arcadis points out that this is paying dividends for the city as "restoration" has "spurred on economic development." In fact, in Arcadis' other sub-index, the "profit sub-index," saw Seoul ranked 18 in the world for wealth and economic health.

Looking after its citizens across income equality, housing, and infrastructure does not just keep the population happy, it also secures more competitiveness longevity.

This is what London is suffering from.

In the same report, while London ranked fifth in its list of wealthy and economically healthy cities, it comes 37 in its people sub-index. This is because of severe social inequality, crime, lack of housing and other major issues that pre-date the EU referendum on June 23.

Arcadis warns that this will threaten London's ability to remain competitive in the future against other huge financial centres across the globe.