Omnicom completes IPG acquisition to become world’s largest agency group

Omnicom Group has officially completed its acquisition of Interpublic Group of Cos., closing one of the most significant deals in the history of the advertising industry and securing its position as the world’s largest agency company by revenue.

The company announced the completion after the U.S. stock market closed on Wednesday afternoon, bringing an end to Interpublic’s 65-year run as the industry’s first major holding company.

A new global leader emerges

With the deal finalised, Omnicom now moves ahead of Accenture Song and WPP to take the top spot among agency groups worldwide.

The acquisition also formally ends one of the longest competitive rivalries in the sector, as Omnicom and Interpublic have operated side by side for decades.

The transaction comes nearly a year after the companies first disclosed their plans to merge, marking a rare consolidation between two of the “big four” global holding companies.

How the deal was structured

Omnicom acquired Interpublic through a stock-for-stock transaction valued at roughly $8.9 billion, according to Ad Age Datacenter’s calculations based on Omnicom’s Nov. 26 share price and Interpublic’s outstanding shares at the end of October. That valuation does not include Interpublic’s debt.

Interpublic shareholders will receive 0.344 Omnicom shares for every Interpublic common share they own. The exchange ratio was fixed at signing last December, meaning the deal’s final value sits significantly below the roughly $13.3 billion headline valuation announced at the time.

Omnicom’s share price has fallen around 31% since the merger announcement, which contributed to the decreased final valuation. Over the same period, Publicis Groupe shares fell 21% and WPP shares dropped about 65%.

The largest acquisition in agency history

At $8.9 billion (excluding debt), the deal nearly doubles the previous record for the largest agency acquisition, Dentsu's $4.9B purchase of Aegis Group in 2013.

It also represents the end of an era as Interpublic, founded in 1960 and widely regarded as the first true holding company in the advertising world, now becomes part of Omnicom.

Once the integration is complete, Omnicom shareholders will hold approximately 60.6% of the combined company, with Interpublic shareholders owning the remaining 39.4% on a fully diluted basis, as reported by Ad Age.

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