Big data provided by a mobile phone carrier backed speculation that Japanese people scaled back efforts to voluntarily refrain from going out to prevent the spread of the coronavirus on the three-day weekend in March, a study has shown.

Crowds of people not much different from normal times were out in Tokyo and other areas during the March break, when cherry blossoms reached full bloom in some parts of the country, according to the study by the National Institute of Informatics (NII), the Canon Institute for Global Studies and others.

Using data from 78 million mobile phones of subscribers to NTT Docomo Inc.’s services and the carrier’s base stations across Japan, the research team, including NII Associate Prof. Takayuki Mizuno, made estimates of how people moved on a region-by-region basis, in a way not to identify personal information, by dividing the country into sections measuring 500 square meters each.

The team gauged the number of people who went out based on the day-night population differences and calculated the percentages of those who exercised voluntary restraint in going out through comparison with figures of normal times, or average numbers for Jan. 6 to 31 this year.

By prefecture, the self-restraint ratio stood at 37.4 percent in Hokkaido on March 1, which was Sunday, right after Hokkaido independently declared a state of emergency. The ratio was the second highest in Tokyo on the same day, at 21.8 percent, and stood below 20 percent in most other prefectures.

On March 20, which was Friday and the first day of the long holiday weekend, when Japanese people are widely said to have scaled back their efforts to stay home partly for enjoying hanami cherry blossom viewing, the voluntary restraint ratio fell as low as 6.9 percent in Tokyo and 6.7 percent in Fukuoka, coming close to ordinary levels.

The restraint ratios rose in the Tokyo metropolitan and other urban areas after the central government declared a state of emergency over the virus crisis for seven prefectures, including Tokyo, on April 7 and for all over the country on April 16.

On Monday, the percentage of people who refrained from going out was the highest in Tokyo, at 53.1 percent, 48.8 percent in Kanagawa and 42.7 percent in Chiba. But the ratios remained below 30 percent in 34 prefectures, such as 10.0 percent in Tottori and 12 percent in Iwate, showing that there were large regional differences.

The research team said that compared to nonurban areas, the chances of interpersonal contact can be higher in densely populated urban areas even if high self-restraint ratios are achieved.

Also pointing to varying extents of self-restraint within the same prefecture, the team stressed the importance of making requests of voluntary restraint that reflect differing regional circumstances.

RELATED PHOTOS People walk in Ueno Park in Tokyo on March 21 to view cherry blossoms. A study shows that people scaled back efforts to refrain from going out during the three-day weekend in March. | KYODO