Jenner will remain as Wavemaker global chief executive.
Organic revenue was up 2.4% in Japan.
Nannette LaFond-Dufour will report to global boss Arthur Sadoun.
Group is forecasting 1-2% organic growth over course of 2024.
North America saw revenues fall by 2.7% for the year, while APAC, Latin America, Africa, Middle East and Central and Eastern Europe grew organic revenues by 3.7%
Group said it was outperforming both ad holding companies and IT consulting peers
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