About two in five American households now subscribe to a video streaming service like Netflix, Amazon Prime or Hulu Plus, according to a new report from the media measurement company Nielsen that tracked the penetration of the digital offerings.

The research sheds light on the popularity of a fast-growing segment of television watching that has been difficult to track because the digital companies release few numbers about how many subscribers they have and what those people are watching. Nielsen, for instance, does not measure the audiences for shows streamed on Netflix or Amazon.

Netflix, which counts 40 million paid subscribers in the United States, ranked at the top in terms of penetration, with about 36 percent of households subscribing to the service in November, Nielsen said Wednesday in its Total Audience Report. Amazon Prime came next at 13 percent during the same period, followed by Hulu Plus at 6.5 percent.

People in households with subscriptions to video streaming services spend significantly more time in front of a screen than those in other households, the figures showed. Homes with the subscription streaming services spend 2 hours 45 minutes a day on time-shifted television seen with video game consoles, multimedia devices, and DVD or Blu-ray players. Homes without a subscription to those services spend 1 hour 57 minutes a day on the same screens.