Twitter is scheduled to release its next earnings report on Tuesday, and arguably the most important metric is monthly active user count. The micro-blogging giant has been unable to please investors on this front as its MAU count has repeatedly come up short of expectations, and this week’s report could reveal just how widespread the issue has become.

Twitter Inc (TWTR) Earnings Preview: MAU Numbers In Focus

How many MAUs does Twitter (TWTR) have now?

Twitter Inc (NYSE:TWTR) said in February that at the end of last year, it had 320 million monthly active users, which came up short of the consensus at 325 million. Verto Analytics pegs the micro-blogging platform’s U.S. monthly active user base at 221.5 million for March, although management didn’t break down its MAU number by domestic and international users in the last earnings release. Based on this metric, Verto assigns a net U.S. reach of 89.5% to the platform.

The firm said Twitter Inc (NYSE:TWTR) had about 93.5 million daily active users, which it said gives the platform a 42% stickiness index reading. Verto estimates that the average Twitter user spends about 2.3 per month on Twitter’s platforms with the average session lasting 3.9 minutes.

PC still the most popular device for Twitter users

The firm said PCs are still the type of device used the most often to access all of Twitter’s properties with 221.1 million users being on PCs. In second place is smartphones with 106.8 million Twitter users, and tablets were in a distant third place at 44 million users. The average PC Twitter user spends 2 hours per month on the platform, while smartphone users spend 1.1 hours and tablet users spend 1.4 hours. Verto CEO Dr. Hannu Verkasalo noted that relying so much on PC users is certainly not a good thing.

“What is worrisome is that most of Twitter’s engagement still comes from PC users (on average 2.0 hours per user per month) vs. mobile platforms,” he said. “They need to drive mobile engagement to be able to leverage the growth fully in mobile advertising in the future. Twitter’s market cap also does not benefit from a portfolios of apps like Facebook or Google are able to benefit from – Vine has 37m monthly users in the U.S. and Periscope 8m – which isn’t bad but is certainly not on par with Instagram, Facebook Messenger, Youtube – some of the major apps owned by the key competitors.”

Interestingly, the generation that’s using the micro-blogging platform the most is Baby Boomers as 31% of Twitter users belong to that generation, putting them only slightly ahead of Millennials at 26%. In third place is Generation Xers, while Silents make up 13% of the user base.

Vine, Periscope among Twitter’s (TWTR) top three properties

Verto reports that the core Twitter platform had 22.1 million users in March, with the average user spending 2.2 hours in 35 sessions during the month, with the average duration of each session at 3.9 minutes. Vine was in second place with 36.6 million users spending an average of 0.3 hours over four sessions per month, with the average session lasting 5.4 minutes. Periscope was in third place with 8.2 million monthly users spending 0.6 hours over eight sessions per month, with each session averaging 4.2 minutes in length.

Twitter Inc (NYSE:TWTR) shares fell 1.74% to $16.94 in afternoon trading today.