What is the average number of people per household?

According to the 2000 National Census, the average number of people per Japanese household is 2.67.
In 1955, the number was about five.
During 45 years, the family size has shrunk and the nuclear family, composed of only a couple and their children, has become the norm.
Estimates for the next century show that Japan's population, which is increasing owing to the longer average life expectancy, will begin to decrease from 2006 because of fewer children being born.