UK agencies outperformed US operations.
Salaries for permanent roles rose just 6% compared with last year, when they were up 10.2%.
Goat has worked with clients including Dell, Beiersdorf, Meta, Tesco, Uber and Electronic Arts.
Mendelsohn and Justin Osofsky given additional remits as a result of the upcoming departure of business officer Marne Levine this summer.
Sorrell underwent surgery on Sunday (5 February).
Changes announced by Daryl Lee.
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