Mobile messenger KakaoTalk's once-overwhelming lead in the instant messaging industry in Korea has continued to falter, as a report Tuesday showed that the number of people regularly using the application has fallen to the lowest figure in 22 months.

The monthly active users -- those who used a service at least once a month -- for KakaoTalk in March was 44.97 million, down from 45.19 million the previous month. It marked the first time the figure for the instant messaging service had dipped below the 45 million mark since May of 2022. South Korea's current estimated population is about 51.6 million.

In December, KakaoTalk relinquished its place as the most-used mobile application in the country when it was dethroned by YouTube, which had 45.65 million monthly active users. YouTube extended its lead over KakaoTalk to just over half a million in March, marking 45.51 million.

YouTube is also the most popular app by far in terms of how long it is used. The accumulated monthly usage time for the mobile version of the video-sharing service was 1.96 billion hours in March, far surpassing KakaoTalk's 548.1 million hours or Naver's 356.8 million hours.

While still the top dog among mobile messenger services here, KakaoTalk's dominance in the market has been trending downward since peaking at 47.07 million monthly active users in April of last year.

According to the report, KakaoTalk accounted for a 39.62 percent share of social networking services, but the figure dropped by 2.6 percentage points compared to February. During the same period, Instagram's share went up by 4.61 percentage points to mark 22.77 percent.

KakaoTalk's slump comes as fewer of its younger users regard it as a favored instant messaging service. A 2023 report by the Korea Press Foundation showed that while 95.3 percent of South Korean teenagers had used KakaoTalk in the previous week, just 59.5 percent said they used it more frequently than other messaging services.

A growing number of teens are instead opting for the instant messaging function of Instagram. The same report showed that 51.3 percent of teens used the Instagram messenger, up from 20 percent in the 2019 report.

The trend can be attributed at least partially to KakaoTalk's past dominance.

The instant messenger is commonly used for work-related communications for those with jobs, as well as class-related communications for students, parents and teachers. As such, more of the younger population is opting to use the Instagram or Facebook messaging services to communication with friends, separating their private life from their official duties.