Netflix remains the biggest road hog on broadband highways — but its overall share of peak-period Internet traffic actually declined slightly over the past six months in North America. And that may be partly due to gains by Amazon, Netflix’s chief rival in the subscription VOD space.

In March 2016, Netflix represented 35.2% of downstream traffic on North American fixed networks during primetime hours, according to a study by network-equipment provider Sandvine. That’s compared with 37.1% six months ago for the world’s No. 1 streaming-video service, and down from 36.5% a year ago.

That doesn’t necessarily mean people are streaming less Netflix video. The decline in traffic share, according to Sandvine’s analysis, most likely stems from the company’s recent improvements in video-encoding efficiency. Last December, Netflix detailed changes in its video-encoding schemes, which the company said could reduce bit rates by up to 20% while delivering equivalent quality.

But part of Netflix’s decline in share of bandwidth consumption may be because of a big jump in usage attributed to Amazon: This spring, Amazon Video accounted for 4.3% of peak downstream traffic, a significant gain from 2% on Sandvine’s report a year ago. Like Netflix, Amazon made optimizations to its video compression in early 2016.

In addition, YouTube also gained share, holding second place on Sandvine’s report with 17.5% share of downstream bandwidth consumed during peak periods (compared with 15.6% last year), as did Hulu with 2.7% this spring (up from 1.9%). The study found a decline in total share of web-browser traffic, which fell from 6% a year ago to 4.2%, and iTunes, which dropped from 3.4% to 2.9%.

Note that Sandvine’s studies don’t report actual bandwidth usage: They compare only relative share of bits delivered over Internet service providers’ networks. So it’s possible that Netflix’s total hours of video streamed actually has increased over the last six months while its content uses less bandwidth.

Meanwhile, Dish Network’s Sling TV now appears among the top 20 applications on most U.S. broadband networks, but it still accounts for less than 1% of peak-period traffic, according to Sandvine. The company defines “peak period” as 7 p.m. to 11 p.m.

Overall, streaming audio and video now accounts for 71% of primetime traffic across North American fixed-access broadband networks — and is expected to increase to 80% by 2020, per Sandvine. The data for Sandvine’s latest report was collected from multiple ISPs in March 2016.

BitTorrent, which in 2008 represented 31% of total Internet traffic, continues to shrink as a percentage of overall bandwidth usage. In March, the file-sharing app accounted for 2.9% of total peak-period traffic (both upstream and downstream) in North America, according to Sandvine, and 5% of total traffic during the day. Storage applications like Dropbox, Apple’s iCloud and Google Drive have surpassed BitTorrent in upstream traffic on fixed networks.