Just 46% of the core TV audience (ages 18 to 58) watch linear TV in a typical month, according to a new Forrester survey of more than 3,000 US online adults. This compares with a slim majority of Gen Xers and Younger Boomers who do so, and 40% of Millennials — the same number as use paid or free online streaming services each month.

As TV habits continue to splinter, marketers must sharpen their ad plans to target audiences by generation, writes Forrester in the new research. For instance, 34% of Millennials spend 4-plus hours per week watching TV online, while just 12% of Gen Xers and Younger Boomers do so. Translation: Millennial-targeted programs must include the online, streamed views in the buy. But with 42% of this group revisiting favorite shows that are no longer on the air, marketers should also consider buying into past seasons from sources such as Hulu Plus.

To learn more about this research, visit the Marketing Leadership blog.