Photo/IllutrationThe Asahi Shimbun

One in four men have never married by their 50th birthday, and the ratio of men and women who remain single their entire lives is continuing to rise, a major study has found.

In an analysis of data taken from the 2015 census, the National Institute of Population and Social Security Research also found that while not as dramatic as for men, one in seven women also remain single until they are 50. The census is taken once every five years.

The study found that 23.37 percent of men never marry, an increase of 3.23 percentage points from the previous study based on the 2010 census. The ratio for women was 14.06 percent, an increase of 3.45 percentage points.

For a long time, the percentage of men and women who never married remained at under 2 percent. That low trend for men continued until 1970 while it remained that low for women until 1960. However, ever since, the numbers of unmarried people have remained on the increase.

The prefectures with the highest ratios of unmarried men were Okinawa at 26.2 percent; Iwate at 26.16 percent and Tokyo at 26.06. Among women, the prefectures with the highest ratios were Tokyo at 19.2 percent, Hokkaido at 17.22 percent and Osaka at 16.5 percent.

Following a separate piece of research, the institute released the results of its National Fertility Survey in September 2016 and found that the percentage of single men between 18 and 34 who said they eventually wanted to marry was 85.7 percent, while the corresponding figure for women was 89.3 percent.

While those figures may be considered high, the survey also found that many of those respondents cited the lack of adequate funds as well as difficulties in finding a place to live as a married couple as obstacles to matrimony.

"The increase in workers who are not hired to full-time jobs for an extended period has had an effect on pushing up the ratio of those who never marry," said an institute official.