Starcom MediaVest Group and The Weather Channel are the first clients to buy direct access to Nielsen Media Research’s minute-by-minute viewership data, Nielsen said Thursday. The data helps advertisers more closely gauge how many people are watching commercials. Nielsen previously analyzed minute-by-minute data for clients who requested such information, but that was a time-consuming and expensive process. “Our clients have made it clear that they need Nielsen Media Research to break the mold to provide information in a more detailed and flexible manner,” said Sara Erichson, general manager of national services for Nielsen.