The rate of people nuclear families from the 2005 population census. The population census classifies in detail the number of household members, and housholds consisting of a married couple only, a married couple with their child(ren), a father with his child(ren), a mother with her child(ren) are calculated as nuclear families. The rate of "households consisting of a married couple and their child(ren)" among "standard households consisting of a married couple" was calculated.

The national average rate of nuclear families in 2005 is 82.77%. This rate is greatest in Tokyo with 92.15%. Tokyo is followed by Kagoshima (91.76%), Osaka (90.77%), Kanagawa (90.48%) and Hokkaido (88.52%). Interestingly, Kagoshima, Hokkaido and Okinawa are also ranked high together with urban areas such as Tokyo, Osaka, Kanagawa and Saitama. There may be some cultural factor in Hokkaido and Okinawa.

On the other hand, Yamagata is ranked last with 57.41%. Other prefectures on the Japan Sea coast such as Akita (64.66%), Fukui (65.36%), Niigata (65.91%) and Toyama (66.84%) have low rates of nuclear families.

In general, the rate of nuclear families is high in urban areas and on the Pacific coast and lower on the Japan Sea coast.

It is highly correlated with the rate of double-income households. This means that the rate of double-incole housholds is high in areas with few nuclear families, from which it can be inferred that the social advancement of women is being supported by family members such as grandparents. It is also highly correlated with Rice Production and the number of people engaged in agriculture, indicating that the rate of nuclear families is low in areas in which the main industry is agriculture.

It is interesting to note that it is also correlated with the number of Daiei stores. There are many Daiei stores in areas with high rates of nuclear families. It can be inferred that Daiei, under reconstruction, is aiming at improving management efficiency by reducing the number of stores and narrowing areas to areas with many nuclear families.