Call it cord cutting. Or call it the rise of Internet video. Whatever you call it, traditional TV viewing has slipped dramatically among viewers between the ages of 18 and 34.

Fresh ratings numbers from The Nielsen Co. (as reported by the New York Post) show that TV usage dropped 10.6% between last September and January. By the end of January, only 17.8 million viewers in the 18 to 34 cohort were watching primetime shows on their TV sets, down sharply from 21.7 million in 2011.

The Nielsen findings support other recent reports of TV's decline. In a benchmark survey, Forrester Research Inc. found that only 46% of respondents between 18 and 88 years old said they typically watched traditional linear TV. For millennials, that number dipped to 40%.

However, the decline in regular TV watching is mirrored by a rise in online video viewing. According to Adobe Systems Inc. (Nasdaq: ADBE)'s 2014 Video Benchmark Report, online TV viewing jumped 388% year-over-year, with numbers rising for both unique monthly views and time spent watching content online. (See Online Viewing Goes Over the Top.)

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For pay-TV providers, the move away from TV sets is a good reason for focusing on multiscreen video delivery. The trend also shows why service providers and programmers alike are experimenting with online-only packages, skinnier content bundles and ad insertion strategies that cut across every type of connected device. (See Verizon Likes OTT Video Prospects, Dish Slings EPIX Online and Multiscreen Video Goes Regional.)

— Mari Silbey, special to Light Reading