SANTA MONICA - The four largest US TV broadcast networks have sponsored a survey to assuage marketers' fears that advertising is less effective because of ad-skipping digital video recorders.
   Researcher Millward Brown's survey for ABC, CBS, NBC and Fox TV claims DVR ownership does not significantly decrease ad recognition.
   Avers svp Michelle de Montigny: "The results are very positive for advertisers. It shows that TV advertising remains as effective as it has been the last two years."