For about two years, Google refused to let Nielsen place measurement tags on ads running on YouTube, a stance that media buyers say stopped some advertisers buying time on the online video site. Last week, Google reversed its position in a decision that analysts say could fuel the shift of TV ad dollars to online video. Nielsen disclosed late last week that Google was allowing advertisers to test Nielsen’s online ad measurement product when they negotiate ad buys on Google’s YouTube. “Following a brief testing period,” Nielsen said, it expects the “measurement tags to be accepted across all Google properties, including YouTube… by early 2014.” Google confirmed the decision Monday. “We know our clients want meaningful measurement, which is why we’re investing in brand-friendly metrics. While we continue to build measurement options powered by Google, we’re also partnering with industry leaders, such as Nielsen and Comscore, to offer objective, credentialed, third-party measurement options.”