NEW YORK: The number of users of over-the-top (OTT) video in the US is growing only slowly with seven in ten internet users already using such services.

During 2015, according to new figures from researcher eMarketer, a total of 181m people in the US will watch video content streamed over the internet, a 4.6% increase on the previous year.

And growth will be even slower in each of the next four years as the total climbs to almost 200m in 2019.

Currently 69.7% of internet users are watching OTT material, a proportion that will edge upwards to 70.4% in 2016 and reach 72.1% three years later.

Nor will that time span see a surge in the percentage of digital video viewers turning to OTT services, as nine in ten already watch video content this way, mostly via YouTube.

This platform will reach 170.7m monthly video viewers in 2015, according to eMarketer estimates – that's 94.3% of all OTT video service users.

Other leading OTT services, such as Amazon, Hulu and Neflix, have lower penetration and, consequently, much faster growth.

A recent survey by Zogby Analytics found that not only were more and more Americans opting to use these alternative OTT platforms but a majority no longer expected cable or satellite TV to be widely used in five years' time.

The number of users of Netflix, for example, is projected by eMarketer to jump 20.4% this year to 114.3m. Growth at Amazon and Hulu is more modest but at 16.2% and 13.5% respectively they still boast significant numbers of users (65.2m and 59.9m).

Netflix penetration of OTT video service users is also well ahead of its rivals. It currently stands at 63.2% compared to Amazon's 36.0% and Hulu's 33.1%.

That lead will be maintained in coming years: by 2019, Netflix penetration will be 71.7%, while that of Amazon will be 44.4% and that of Hulu 41.2%.

Data sourced from eMarketer; additional content by Warc staff