Netflix is leaving an indelible mark on the TV biz — and while the streaming giant isn’t dealing a fatal blow to the industry, it is seriously cutting into traditional television ratings.

In 2015, Netflix accounted for about half of the overall 3% decline in TV viewing time among U.S. audiences, according to a new study by Michael Nathanson of MoffettNathanson. The analyst calculated that based on an estimate that Netflix’s domestic subs streamed 29 billion hours of video last year (Netflix said members worldwide watched 42.5 billion hours in 2015). That would represent 6% of total American live-plus-7 TV viewing reported by Nielsen (up from 4.4% in 2014).

Moreover, Nathanson predicts Netflix’s total streaming hours as a percentage of TV viewing will continue to rise to about 14% by 2020. “Currently, Netflix is a source of industry pain, but not necessarily a cause of industry death,” he wrote in the note.

Executives at media conglomerates are now viewing Netflix as a growing threat. Time Warner CEO Jeff Bewkes, who once compared Netflix to the “Albanian army,” last fall said that the company may pull back on licensing TV content to SVOD services.

But not all TV networks are suffering from the rise of Netflix and other streaming-video services, Nathanson noted. Total viewing of networks from Time Warner, Scripps Networks Interactive, AMC Networks and Discovery Communications rose in 2015. A+E Networks’ viewing hours declined 15%, Viacom fell 13%, and NBCUniversal and Disney each dropped 5% overall.

In comparing TV viewing of Netflix vs. non-Netflix households, broadcast networks took the biggest hit in 2015. CBS viewing among Netflix subs was 42% lower than non-subs, with Fox at -35%, ABC at -32% and NBC at -27%, according to Nathanson’s analysis.

Meanwhile, viewing time of Disney’s networks last year was 11% higher in Netflix homes versus non-Netflix homes. Viacom saw a “modest” 5% year-over-year drop in Netflix homes; in that case, “it is unclear if this is as a result of viewership which has already been negatively impacted by SVOD services in prior years, or if the company’s younger-skewing viewers are switching back and forth more easily to watch both linear television and SVOD services,” Nathanson wrote.

Based on viewing time, Netflix in 2015 was bigger than smaller cable programmers like A+E and AMC, but not as large as the seven biggest conglomerates (NBCUniversal, Disney, Viacom, Time Warner, 21st Century Fox, Discovery and CBS).

One caveat on the analysis: Nielsen’s Live+7 excludes online and mobile viewing on TV networks’ sites and apps. But Nielsen hours-viewed numbers adjust for co-viewing, whereas Netflix’s reported data is per household. According to Nathanson, that means Netflix per-person viewing is underrepresented relative to Nielsen Live+7; thus, the analyst assumes the two factors largely cancel each other out.

Other studies have compared Netflix’s viewing to traditional TV. The service was on track to attract a larger 24-hour audience than each of the major broadcast networks (ABC, CBS, Fox and NBC) some time in 2016, per an analysis last summer by FBR Capital Markets.

As of the end of 2015, Netflix reported 74.76 million streaming customers worldwide, including 44.74 million in the U.S.

One big challenge for Netflix now will be increasing its reach among older consumers, according to Nathanson, an age group that watches more traditional TV than younger demos. SVOD penetration among those 35-44 is 60%, then tapers off to 54% for the 45-54 cohort, 37% for 55-64 and 23% for those 65-plus.

Nathanson’s note Thursday, “Is Netflix Killing TV?,” is an update to one the analyst published last April.