Amazon's huge investments in streaming programming seem to be paying off.

Amazon Prime Instant Video, the Netflix-like streaming video service that comes as part of Amazon's $99 per year Prime loyalty program, continues to grow. Its share of Internet traffic being piped into homes during peak times -- roughly 7 p.m. to 11 p.m. -- has more than doubled in the last 18 months, from 1.27 percent in March 2013 to 2.58 percent in September, according to a new report from Sandvine, a company that makes broadband network equipment and sells it to Internet providers.

Prime Instant Video is nowhere close to Netflix, which continues to account for more than one-third of traffic going to American and Canadian homes during peak evening hours. Yet Amazon's growth suggests that the company's increased spending on video and perhaps even its streaming hardware is bearing fruit.

The figures, which Sandvine releases in a report twice each year, offer a rare glimpse at how much people are watching Netflix, Amazon and other streaming services, which are notoriously tight-lipped when it comes to viewership data.

Amazon has not said how many Prime members it has -- one analyst pegs it at 30 million to 40 million in the U.S. -- though people tend to sign up for Prime primarily for the free two-day shipping. Amazon Prime Instant Video isn't available in Canada. Netflix has more than 36 million paying members in the U.S., though the company doesn't say how many it has in Canada.

Sandvine's report comes as Amazon has been investing heavily in Prime and Prime Instant Video. Amazon this year signed a deal with HBO to add some HBO shows to its Prime Instant Video catalogue. The deal was rumored to cost Amazon more than $300 million for three years of shows. Amazon also saw critical acclaim with its original series "Transparent," a comedy/drama starring Jeffrey Tambor that came out in September.

Amazon has been beefing up its Prime benefits of late. Prime members spend more money, shop more frequently and buy more expensive items than non-members, so Amazon has been sweetening the pot to get people to join. This year, Amazon has added unlimited photo storage, a streaming music service as well as discounts on Amazon hardware to Prime membership.

Amazon this year also came out with two new media players that you connect to your TV to stream programming from the Internet. Amazon's Fire TV streaming box went on sale in April, and its recently announced Fire TV Stick began shipping on Wednesday.

The world of streaming video is about to get a lot more crowded. HBO and Showtime recently announced that next year, the premium TV networks will offer standalone versions of their services. They are aimed at so-called cord cutters, the growing number of people who don't pay for cable or satellite TV, and instead get entertainment through services like Netflix, Hulu and Amazon.

"They're not in the next year going to be at the same level as Netflix, but they're certainly going in the right direction," Dan Deeth, media and industry relations manager at Sandvine, said of Amazon. "HBO will be a very interesting player in this next year."