Rotorua has more houses than it did 100 years ago but there are fewer people living in them, Statistics New Zealand data shows.
It shows the city has only about 2.6 people per household.
This fits in with the national trend of 2.7 people per household, which is nearly half the number of people per household in 1886, when 5.2 people was the average.
First National principal Ann Crossley had not noticed families were shrinking but said people's living arrangements were changing.
"I guess in that century there will be family living with extended family, whereas that doesn't happen as much any more.