In brief: It's been around a year and a half since Elon Musk took full control of his favorite social media site, Twitter. The billionaire has made a ton of changes during this time, including changing the platform's name to X. How has that impacted users in the United States? According to a new report, the number of daily users in the country has fallen by around a fifth during Musk's time in charge.

According to data from market intelligence firm Sensor Tower (via NBC News), X's US user base has been declining every month since Musk's first full month in charge. The 27 million daily active users it had in February marked a 27% decline compared to November 2022. It's also down 18% from the same period a year earlier.

Sensor Tower adds that X's global user numbers have also fallen, though not as much – by 15% to 174 million. Its worldwide user figures have been flat or declined every month during Musk's reign except for one.

Musk might take solace in the fact that while X has seen the largest decline among the big social media apps, all its rivals' US user numbers are down compared to November 2022. TikTok saw the second-largest fall, down 9.5%, followed by Instagram (down 4.4%), Snapchat (down 1.7%), and Facebook (down 0.6%). Unlike X, all the apps saw their global user numbers grow during the same period.

X has refuted Sensor Tower's claim. The company said 250 million people use the platform every day, with 550 million visitors each month. X added that both the daily average time spent on the platform and daily active user minutes are up year on year. Musk responded with a post on X pointing to the decline in "legacy media" users. On Sunday, he asked X users to send links from the platform to friends who are "still being misled by the legacy media."

Back in January, mutual fund firm Fidelity, one of the financial backers behind Musk's acquisition of X, said it believed the company was worth 71.5% less than the $44 billion it was worth at the time of Musk's purchase. Fidelity now values the firm at just over $12.5 billion.