Havas Advertising has joined the Ad Age/Bloomberg AdMarket 50 index, taking the slot held by Young & Rubicam
's absorption last week by WPP Group. Paris-based Havas began Nasdaq trading in September when it acquired Snyder Communications, adding Snyder units including Arnold Communications and Brann Worldwide to its holdings. Since opening at more than $17 in Nasdaq trading, Havas' share price has drifted lower. In trading Friday, it closed at $15.19, up 3.85% for the week.