CAMBRIDGE, MA: One in five US adults are "cord-nevers" – people who have never had a cable subscription – and that proportion will rise to one in three among Millennials by 2025, a new study has predicted.

A survey of 32,000 US adults by Forrester Research found that 76% currently subscribed to cable; and among the 24% who didn't, just 6% were classed as "cord cutters" who had ended their subscription, while 18% had never had one, Ad Week reported.

This year is something of a turning point, noted Forrester analyst James McQuivey, as the proportion of cord-nevers passes that of cord-cutters, a development he described as "the next stage of evolution in TV viewing".

CMOs must experiment on these groups now, he advised, in order to learn how to serve them later.

Older viewers remain committed to cable, however, with 80% of those over the age of 32 subscribing in 2015, with 15% being cord-nevers and 5% cord-cutters. The equivalent figures for 18-31 year olds show 65% subscribing, 25% being cord-nevers and 10% cord-cutters.

Forrester expected that in ten years' time just 50% of the younger age group would still have a cable subscription while 35% would never have had one and 15% would have cut the cord.

"Rather than inherit TV viewing expectations from a prior era and then consciously reject them, as cord cutters have done, these cord-never viewers have simply bypassed prior assumptions, exhibiting nearly the exact set of behaviors that cord cutters have pieced together for themselves over the past decade of viewing," McQuivey said.

In terms of viewing time, cord-nevers watch almost twice as much streaming video as those with cable, at around eight hours a week compared to the latter group's 4.6 hours. Cord-cutters, however, are the most enthusiastic viewers, on 10.2 hours.

Earlier this year research firm SNL Kagan reported that pay-TV operators in the US had lost 625,000 video subscribers in the second quarter, which was the largest quarterly drop on record.

It's a trend that will not be reversed, given the growing number of options open to viewers. In response, networks like HBO and CBS have already launched standalone, online streaming services.

Data sourced from Ad Week; additional content by Warc staff