The 10 biggest ad agencies in the world, post-Publicis, Omnicom merger

American and French advertising companies the Omnicom Group and Publicis Groupe have announced their plans to merge and form an ad powerhouse with an annual revenue of $22.7 billion and a stock market value of $35.1 billion. If the deal, expected to be sealed in the fourth quarter, does go ahead, it would create the world's largest ad company with greater clout to negotiate ad rates with clients.

With the advertising world likely to see a new giant, let's take a look at the 10 biggest advertising agencies in the world.

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WPP

Headquarters: London

Country: The United Kingdom

Revenue: $15.6 billion

Number of employees: 165,000

Major clients: Colgate-Palmolive, HSBC and Vodafone

Overall rank: 1

WPP, the world's biggest advertising company, employs 165,000 in 3,000 offices spread over 110 nations. It traces its roots to 1985 when Martin Sorrell, the current CEO, bought a stake in Wire and Plastic Products, a producer of wire baskets, while looking for a company to launch marketing services around the globe. Over the decades, WPP bought and sold stakes in several firms, including some major rivals, and emerged as a powerful force in the advertising world.

Although occupying the top spot, it has faced some controversies, such as allegations of going to great lengths to pay lower taxes in the United Kingdom and a revolt by shareholders over Sorrell's salary.

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Omnicom Group

Headquarters: New York City

Country: The United States

Revenue: $14.3 billion

Number of employees: 70,600

Major clients: PepsiCo, AT&T and Microsoft

Overall rank: 2

Omnicom Group, a major advertising and marketing communications services company founded in 1986, manages more than 1,500 agencies and 5,000 clients in 100 countries. Once it was a big investor in Internet technologies, but began avoiding such investments after the dotcom crash. 

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Publicis Groupe

Headquarters: Paris

Country: France

Revenue: $7.7 billion

Number of employees: 60,000

Major clients: Gucci, Hermes, LVMH

Overall rank: 3

Publicis was started by Marcel Bleustein in 1926 in Paris when he was just 20. He selected the name Publicis as it mixes the French words for "advertising" and "six", his favourite number. Now it has presence in 108 countries, employs about 60,000 employees and has a 26 per cent market share in emerging nations.

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Interpublic Group of Companies

Headquarters: New York City

Country: The United States

Revenue: $6.693 billion

Number of employees: 7,494

Major clients: General Motors, Johnson & Johnson, Microsoft and Unilever

Overall rank: 4

Interpublic Group of Companies, the world's fourth-biggest ad agency, has been plagued with problems since early 2000. It began with some ill-timed acquisitions in the United Kingdom's motor-racing world and then became embroiled in accounting scandals. By mid-2000, it had disposed of several loss-making entities and its stock slowly stabilised.

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Dentsu

Headquarters: Tokyo

Country: Japan

Revenue: $3.1 billion

Number of employees: 14,898

Clients: Kraft, Canon and Toyota

Overall rank: 5

There are many advertising companies in the world, but none dominates its home markets like Dentsu rules its base, Japan. It controls more than 30 per cent of the Japanese market, has 6,000 clients and is twice big as its closest competitor. In recent years, it has made a serious bid to capture markets outside Japan through acquisitions and deals.

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Havas

Headquarters: Puteaux

Country: France

Revenue: 1.77 billion euros

Number of employees: 15,000

Clients: Air France, Citigroup, IBM

Overall rank: 6

Havas, one of the largest groups in the world, is present in more than 100 countries through its networks of agencies and contractual affiliations. Employing 15,000 people, it offers range of communications services, including digital, advertising, direct marketing, media planning and buying.

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Hakuhodo

Headquarters: Tokyo

Country: Japan

Revenue: 1.2 trillion yen

Number of employees: 3,043

Clients: Apple, Nissan and Suzuki

Overall rank: 7

Hakuhodo was founded in 1895, making it the oldest advertising agency in Japan. Its main areas of function include brand management, TV commercials and newspaper ads and strategy planning. It has spread its footprints all across the world, including Asia and the United States.

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Merkle

Headquarters: Lanham

Country: The United States

Revenue: $300 million

Number of employees: 1,700

Clients: Walmart, Dell and Novartis

Overall rank: 8

Merkle, which was bought by current CEO David Williams for $5.2 million in 1988 when he was 25, has built up a strong base through strategic acquisitions over the last two decades. With more than 1,700 employees, the privately-held customer relationship marketing group is now constantly ranked as one of the leaders in the field.

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Global Experience Specialists

Headquarters: Las Vegas

Country: The United States

Revenue: $249.3 million

Number of employees: 165,000

Clients: Nike, Philips and Dove

Overall rank: 9

Global Experience Specialists, one of top providers of exhibition, conference and event services in the United States, Canada and the United Kingdom, was created in 2010 after merger of three units. It is part of the Viad Corporation with 60 offices around the world.

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Epsilon

Headquarters: Dallas

Country: The United States

Revenue: $898 million

Number of employees: 5,000

Clients: Ford, General Motors, P&G

Overall rank: 10

Epsilon's story started in 1975 when four Harvard students created a database to store the contact information of fellow students. It is now the biggest marketing agency in the United States. Its main role is to help clients better manage their customers.