The estimated populations of two cities in Ishikawa Prefecture, which were hit by a powerful earthquake and torrential rain last year, have dropped by about 30 percent each, according to an analysis by a Japanese technology venture.

LocationMind, launched by researchers at the University of Tokyo, used anonymized location data from mobile phones provided by the Japanese telecom firm NTT Docomo to analyze changes in the populations of the cities of Wajima and Suzu.

Its analysis estimates that Wajima's population dropped by 30 percent and Suzu's by 37 percent. It compared figures from December 2023 and November of last year, which are before and after the quake.

The company counted those who stayed at the 2 cities for a certain period of time as residents, adding possible numbers for people who do not have mobile phones.

The drop is in stark contrast with prefectural statistical figures, which estimate the municipal population every month based on data such as residential certificates. It shows the population of Wajima and Suzu each fell by 9 percent from last January through last November.

LocationMind indicated that some people may have left the city without updating their certificate of residence, adding that the actual population is likely shrinking more than what prefecture estimates.

The company's CTO, Shibasaki Ryosuke, said it is important to accelerate reconstruction works as soon as possible for those who have left their hometowns, as it will get more difficult for them to return as more time goes by.