Advertising giants Omnicom and Publicis said Sunday they had agreed to merge, in a $35.1 billion cross-border linkup that shows how Big Data is making Madison Avenue look more like Wall Street.

The combination of Omnicom Group of the U.S. and France's Publicis Groupe SA is aimed at restoring the balance of power between advertising agencies and such Silicon Valley companies as Google Inc. and Facebook Inc. About 22% of global ad spending now is digital, according to eMarketer, a share projected to grow to 27% by 2017.

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