The institute has been conducting opinion polls every five years since 1973 to learn about people's views on family, life and work.
It surveyed 2,751 people in 2018 between June 30th and July 22nd. Respondents were all above the age of 16, chosen at random nationwide.
Fewer people think marriage or having children necessary
The results are bad news for a government that's trying to boost the birthrate. A record 68 percent of the respondents said "a person does not necessarily have to get married." That's five points higher than in the last survey.
And a record number of respondents said they don't believe married couples need to have children. The number hit the 60-percent mark for the first time. These views were more common among younger respondents than older ones.
Those ideas appear to be playing out in terms of the birthrate in Japan. The health ministry estimates there will be 921,100 births in 2018. That's down 25,000 from 2017, and the lowest since record-keeping began in 1899.
Image of ideal family changing
The number of respondents who believe women should go back to work after having children has been rising steadily. It hit the 60-percent mark for the first time in 2018. Just eight percent of respondents said women should focus on family once they get married.
When couples do have children, men are expected to take a greater role in raising them. Nearly 90 percent of respondents said they thought "fathers should commit to household work or take part in child rearing." In 1973, when the survey started, just over half of the respondents felt that way.
The survey also suggests people have higher expectations for girls' education. Assuming respondents had a daughter in junior high school, the survey asked what level of education they would hope for her to achieve. Sixty-one percent said "university level." That percentage has been rising steadily since the 1980s. Still, Japan is one of only three industrialized countries that sends more men than women to university. The other two are South Korea and Turkey.
The Ministry of International Affairs says a record 74.3% of women between the ages 15 and 64 were employed in 2017. That's the highest percentage since the government began keeping track in 1968.
Yokohama National University professor Yumiko Ehara says the role of women in society has been improving steadily over the last half century, regardless of how the economy was faring. But she says the employment figures don't paint the full picture, since many women are in relatively unstable conditions and work for lower wages than men.