DENVER (KDVR) — Declining public school enrollment could have something to do with fewer kids being born.

Coloradans have been having fewer and fewer kids over the last 20 years. The issue is especially pronounced in the two counties that have closed schools in the last week — Denver and Jefferson counties.

Jefferson County is closing 16 of its schools after a decade of enrollment loss. The district only serves 69,000 students out of its allotted space to serve 96,000. Denver Public Schools has announced a list of 10 elementary and middle schools recommended for closure as the district faces major declines in enrollment.

Both Denver and Jefferson counties have had worse luck with falling birth rates than other metro counties.

Colorado has seen a steady drop in the number of annual births since 2008 when the annual number peaked at just over 70,000. Since then, the number of Colorado births dropped 13%.

Most metro counties saw their births peak in the late 2000s, but Boulder, Denver and Jefferson counties peaked in 2001. Their birth rates have been falling for longer than other metro counties.

Fewer babies mean fewer kids in classrooms. The number of children in each county who are school age has fallen along with the overall birth rate.

In 2001, about 17% of Denver was school age, which is between the ages of 5 and 18 years old. Last year that number shrank to 15%.

Jefferson County, which has lost more students than Denver Public Schools through the COVID pandemic, has also lost more of its school age population. In 2001, 22% of Jefferson County was between 5 and 18. Last year, that had dropped to 17%.