Rights holders now confirm that the Apple Music’s paid subscribers are at about 32 million.

What’s more, the service enjoyed some 40.7m unique users in March, leading all U.S. streaming services, according to a survey from global media-measurement shop Verto Analytics. Next came Pandora with 32.6m, followed by Spotify (30.4m). That larger number may shade over into iTunes use, as it’s based on analysis of sessions within the Apple Music app, which may include some downloaded/MP3 music.

Verto’s opt-in consumer survey—of the Top 10 services among adults 18+—surveyed only mobile users; with MacBook users factored in, the Apple Music overall user base is thought to be in the neighborhood of 41m (including free trials).

(click graphic to view survey; download it here)

Verto’s survey also reveals that Amazon Music, while ranked sixth, boasts some 13.4m monthly users and also a high “stickiness” rating (22%). The latter is based on comparing daily to monthly users as a measure of overall engagement. Spotify leads among large contenders with 25% stickiness, while Pandora radio rates a 21%. Tidal, which has too small a user base to make the leaderboard, also fares well in the stickiness sweepstakes—the study notes that fewer users can add up to greater stickiness (this is also true of on-demand also-ran YouTube Music). iHeartRadio and SoundCloud were the other U.S. streaming leaders.

We asked Verto about their methodology and they told us that they define active users as “users that are actively and routinely using an app or service within a certain time period (day part, daily, monthly etc.).” Panelists’ activity is tracked on all platforms and devices via a measurement app. This data is then combined with info from advertisers, content distributors and other aggregators. Number of sessions per user per month is the primary indicator of user engagement in calculating the rankings.