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Meridian’s growing fast – but Boise’s growing slow: New population estimates for Ada & Canyon counties


Have you heard?

The Treasure Valley is growing.  Acording to the Community Planning Association of SW Idaho (which goes by COMPASS), Ada and Canyon Counties added 23,890 new residents from 2020 to 2021.

The numbers are not official and are a sort of home-brew formula COMPASS devised. It looks like this:

Population = [(h + r) * s * o)] + q 

Put in non-mathematical formula terms, the group takes the 2010 US Census and extrapolates based on new residential units, the average household size, occupancy, and other factors to come up with an estimate.

Overall population for Ada and Canyon counties

The data shows the Ada and Canyon County region stands at 761,680 residents – up from 737,790 people the year before. That’s a growth rate of 3.24%, or 23,890 new folks over the last year.


The estimates show growth of course. But looking at the numbers over the past ten years, the total number of new folks who moved in in 2021 is less than moved in during the years 2020, 2019, or 2015.

The growth rate stood at 3.24% – or less than 2020, 2019, 2015 or 2014.

Of the nine cities over 10,000 residents:

Growth for the county’s nine largest cities
  • Star grew the fastest on a percentage basis from 2020 to 2021 – adding 13% to its population base, or 1,540 new residents. 
  • Meridian grew the fastest in terms of the newest residents – adding 8,540 additional people, or a growth rate of 7.16%.
  • Boise saw the slowest growth on a percentage basis and total number of new residents from 2020 to 2021 among the cities over 10,000 residents.  Just 1,210 new residents joined the City of Trees, or a growth rate of .5%.

Comparing 2010 to 2021

While all 14 cities and the unincorporated areas of Ada and Canyon County saw growth from 2010 to 2021, the population distribution changed a bit.

In 2010, 35% of all Ada and Canyon residents lived in Boise.  Today, that number stands at 32%.  Meridian went the other direction – growing from 13% of the population in 2010 to 17% in 2021.

Changes in population distribution, 2010 and 2021

That’s due in large part to growth rate.  From 2010 to 2021, Meridian added 52,798 residents – a growth of 70%.  During the same period, Boise grew by 35,919 people, or a rate of 17.5%

But while Meridian added the most residents on a gross basis, it didn’t grow the fastest on a percentage basis.  

  • Star jumped from 5,793 people in 2010 to 13,400 in 2021 – a growth rate of 131%.  
  • Kuna boomed from 15,210 residents in 2010 to 27,570 in 2021, an 81% growth rate.
  • Eagle popped from 19,08 folks in 2010 to 34,470 in 2021, growing 73%.
Don Day - BoiseDev Editor & Founder
Don Day - BoiseDev Editor & Founder
Don is the founder and publisher of BoiseDev. He is a National Edward R. Murrow Award winner and a Stanford University John S. Knight Fellow. Contact him at [email protected].

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