"Measurement is one-third to one-half of it," Bewkes said in an interview held before investors at the UBS Media and Communications Conference in New York.
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Sure, Bewkes said, the popularity of subscription video services led by Netflix (NFLX) and Hulu and Amazon's (AMZN) Prime service, is partly to blame but he didn't "think it's that much."
Rather, the culprits are more people viewing television beyond the measured time periods, time-shifting, the delayed watching of shows using DVR devices, and the inability, so far, of Nielsen to adequately measure digital platforms outside of traditional monitoring. Television's lower viewership numbers, he said, aren't reflective of some historic shift of viewers choosing online over TV.
"We just don't think the viewing numbers are part of a secular trend," Bewkes said.
But lower overall ratings are a reality. Third-quarter viewing of ad-supported television fell 4% during the third quarter, compared to the same period a year earlier, according to media analyst Todd Juenger of Sanford C. Bernstein in a study of data from Nielsen. Data from Rentrak showed the decline at 7%, Juenger wrote in a report last month. Among younger adults, the declines were even greater.
As for cable-TV, Nielsen's third-quarter numbers revealed declines almost across-the-board, and by double-digit percentages. Time Warner's TNT and TBS networks recorded ratings that were 13% lower than for the same period a year earlier, according to data compiled by MoffettNathanson.
CBS (CBS) CEO Leslie Moonves didn't deny the lower ratings but countered that CBS hasn't been as nearly effected as his rival broadcast networks. While Disney's ABC is doing comparatively well from a year ago, Comcast's (CMCSA) NBC is coming off a blockbuster Olympics while 21st Century Fox (FOXA) doesn't have much to sell given its acute ratings problems.
Given the terrain, Moonves purported to take the high road, downplaying any frustration with Nielsen, which continues to rate CBS as the country's most-watched. "We are winning the game, so we're not going to challenge the referee," he said.
As for the decline in advertising dollars being spent on television, Moonves countered that the industry is still around $70 billion and that the majority of that money goes to the Big Four networks. Rather than losing money to digital, Moonves insisted that digital is gaining at the expense of print and niche cable-TV channels.
"It takes a lot of hits on YouTube to equal one NCIS," he said, referencing one of CBS' most successful franchises.