 The total Swiss population change in 2008 (from all sources, including moves across municipal borders) was an increase of 5 and the non-Swiss population change was an increase of 20 people.This represents a population growth rate of 1.2%.The age distribution, , in Castel San Pietro is; 175 children or 8.4% of the population are between 0 and 9 years old and 200 teenagers or 9.6% are between 10 and 19.