Idaho’s population growth has been growing fast – so quickly that the state had the No. 1 growth rate in the nation at 21.5 % from 2012-2022, according to the U.S. Census Bureau.
Close to 90% of the state’s population growth stems from rapid net domestic migration into Idaho and not from Idaho residents suddenly deciding to have lots of babies. Idaho’s birth rate of 11.8 births per 1,000 population in 2021 (12th highest in the nation) was a 29% decline compared with 16.6 in 2007, fourth highest in the nation at the time). The rate remains higher than most of Idaho’s bordering neighbors, such as Oregon at 9.6 (fourth lowest), Montana at 10.2 and Washington at 10.8. Nationwide, birth rates per 1,000 population have decreased 23%, from 14.3 in 2007 to 11.0 in 2021 .
Migration is contributing to a higher number of school-age students in Idaho today than expected based on Idaho births alone but is still unable to reverse the trend that Americans in general are having significantly fewer babies than in the past.
The short-term upside of fewer babies means more women are able to be active participants in today’s labor force, but that benefit will be more than offset as the population continues to age. Birth rate patterns dropped significantly beginning in 2009, continued through 2022 and are expected to continue to fall. This will have an adverse impact initially on primary and secondary school enrollments, followed by a reduction of Idaho’s future labor force as fewer students reach working age.
Idaho’s annual births and school enrollment Levels
Over the past 20 years, Idaho’s statewide population increased 45%, from 1.34 million in 2002 to 1.94 million in 2022 . However, despite this robust growth, total births per year have not kept pace. While Idaho’s population increased by more than half a million residents since 2002, births increased only 7% (1,500), from 22,382 in 2022 compared with 20,973 births in 2002 . The highest number of births for the years 1997 – 2022 occurred in both 2007 and 2008 with more than 25,000 births statewide each year.
Most of these babies would have been conceived either before the official start of the recession in December 2007 or during the very early stages of the recession in the first few months of 2008. As the recession continued to deepen throughout the economy over the next couple of years, Idaho births would plummet to only 23,000-24,000 per year in 2009-2010, dropping further to remain consistently below 23,000 since 2011. Within the time series of 2002-2022, Idaho had fewer than 22,000 births per year in 2002, 2003, 2018 and 2020. If this trend was due solely to the recession, births would have bounced back to previous trends when the economy started growing again. However, this has not been the case as the number of births remain stagnant while overall population numbers increase.
From 2019-2022, Idaho’s average annual population growth of 2.8% was more than five times faster than births at 0.5%. Since 2010, Idaho’s population has been growing at an annual rate of 1.7% per year while the annual number of births actually declined by -0.4%. Cumulatively, the state’s population has grown 57% between 1997-2022 compared with annual births rising only 21%.
This same trend can be seen regionally. From 2007 to 2021, the birthrate dropped from 17% in northern Idaho to a high of 31% in eastern Idaho.
Combining birth data with public school enrollment by grade shows a similar pattern, even though school enrollment numbers are higher than the corresponding birth year due to Idaho’s positive net migration gains. In Idaho, ninth graders numbered the largest class by enrollment in 2022-2023 with more than 26,000 students, most who would have been born between September 2007 and August 2008. The smallest enrolled class in Idaho (excluding kindergarten) was first grade with just over 23,000 students. The difference of approximately 3,000 more students in ninth grade than in first grade is the equivalent of 150 fewer 20-pupil classes statewide.
The following chart compares Idaho’s public school enrollments by grade in 2022-2023, with the births in Idaho for the corresponding grade year. The difference between the lines can be attributed to net domestic migration into Idaho but does not account for students not enrolled in the public school system who attend private school or are homeschooled. Although current school enrollments by grade are higher than birth levels would predict them to be, both lines show a very clear downward trend after peaking in 2007-2008.
Source: CDC Vital Statistics, Idaho State Board of Education
Only 10% of Idaho’s total population growth from 2019-2022 was from youth aged 0-17. In 2019, when the U.S. Census estimated Idaho’s population at nearly 1.8 million and 448,000 residents were under the age of 18. This population of residents aged 0-17 represented the third highest ratio in the U.S. at 25.1% of the total population.
As of 2022, Idaho’s percent of its population under age 18 was ranked sixth nationally after falling to 23.9%. Twelve of Idaho’s 44 counties reported population declines for the number of residents under age 18 in 2022 compared to 2019. Surprisingly, 90% of Idaho’s population growth from 2019-2022 was from adults over the age of 18, not students who would be enrolling in Idaho’s local school districts.
By region, one-third of the state’s total population growth under age 18 was in northern Idaho at 33% with southwestern Idaho close behind at 31% and eastern Idaho next with a 22% gain. Together, these three regions accounted for 84% of Idaho’s total population growth and 86% of the growth for youth under age 18 over the past three years. While north central Idaho realized the smallest population growth in this period at 3% of the total, southeastern Idaho witnessed the slowest growth in those under age 18 at only 2% of the statewide growth. 2021 birth rates throughout the state range from a low of 10.1 in north central Idaho to a high of 14.9 in the eastern region. As the northern region’s birth rate is one of the lowest in the state at 10.2, the recent growth rate of youth within this area can largely be attributed to migration.
If this lopsided growth pattern persists, fewer classrooms will be needed in the future and the ratio of residents reaching retirement age in Idaho will be noticeably larger than those either entering school or reaching age 16 and being considered part of Idaho’s labor force.
Many other elements affect current and future school enrollment in Idaho, such as virtual v. in-person school, private/charter v. public schools, four-day v. five-day school weeks and rural v. urban environments. More on these elements will be examined in another article to be published soon.
 CDC, Vital Statistics
 US Census Bureau, Annual Population Estimates
 Idaho Department of Health and Welfare, Vital Statistics