After two years of measuring Netflix viewing, Nielsen has now added Amazon Prime Video to the mix of subscription-streaming services it tracks — and with the same set of limitations.

Nielsen’s SVOD Content Ratings originally launched in October 2017 with Netflix. According to the research firm, the addition of Amazon Prime Video measurement will let Nielsen’s clients better analyze their own content consumption on Prime Video as well as the total content lifecycle of competing media.

However, as with its Netflix metrics, Nielsen is looking at only a portion of Amazon Prime Video viewing. The company’s SVOD Content Ratings measure only connected-TV viewing (excluding mobile devices and desktops) and the service covers only the U.S. — whereas both Netflix and Prime Video are available in most countries around the globe.

Nielsen released data points for one Amazon Prime program: “The Boys,” the genre-bending superhero show produced by Sony Pictures Television. According to Nielsen, in the first 10 days of its premiere date (July 26-Aug. 4), “The Boys” reached nearly 8 million viewers over its eight-episode season. The average audience size of “The Boys” over that time period was 4.1 million people with an average of a little over 6 million viewers tuning in to the premiere episode. Nielsen also said 39% of the total average audience was comprised of viewers 35-49, the largest age demo over the 10-day window.

In “The Boys,” based on the bestselling comic of the same name by Garth Ennis and Darick Robertson, superheroes are as popular as celebrities, as influential as politicians, and as revered as Gods. But they also abuse their superpowers rather than use them for good. Enter the titular Boys, who set out to expose the heroes and the multibillion-dollar conglomerate that backs them for who they really are. Amazon renewed the show for a second season ahead of its premiere.

Despite the limitations of Nielsen’s SVOD measurement, it seems that some in Hollywood believe that even a limited independently-sourced picture of the opaque world of subscription-streaming viewing is better than none at all.

James Petretti, Sony Pictures Television’s SVP of U.S. research and analytics, called Nielsen’s SVOD measurement “invaluable for our studio to understand how our programs perform on these platforms and the audiences they attract.”

“Nielsen has the ability to help us understand what these audiences are doing outside of those platforms as well — how and what they are watching on other on-demand and linear services,” Petretti said in a statement. SPT also is able to gauge the impact of traditional linear TV advertising in driving viewers to SVOD programs, he added.