FTSE 100 media group WPP on Tuesday announced that its wholly-owned media investment management company, GroupM, has acquired 49% of US media agency Haworth Marketing + Media.In the year ended 31 October, the firm's billings totalled $700m with gross assets of $87m at the period end.GroupM's clients includes Target, Ben & Jerry's, Beats by Dr. Dre, DreamWorks Animation and The Oscars.Founded in 1970, it currently employs around 140 people."The investment continues WPP's strategy of investing in important markets such as the US where WPP companies (including associates) collectively generate revenues of over $6bn and employ approximately 25,000 people," the group said.