But the expected growth isn’t necessarily equal. In Utah and Weber counties, for instance, different dynamics are at play. Utah County’s younger population bodes for more pronounced population increases, a University of Utah demographer says, while Weber County’s older population bodes for slower growth.

“Weber County and Utah County are pretty different demographics,” said Emily Harris, a demographer for the University of Utah’s Kem C. Gardner Policy Institute.

Indeed, a look at the figures shows disparate growth rates among Utah’s four most populated counties along the Wasatch Front. The estimates come from the Kem C. Gardner Policy Institute:

• Utah County’s estimated 2015 population of 585,694 is expected to grow to 1.08 million by 2040, up 84.4%, and to 1.62 million by 2065, up 176.6% in the 50-year span.
• Davis County’s estimated 2015 population of 336,091 is expected to grow to 451,924 by 2040, up 34.5%, and to 544,958 by 2065, up 62.1%.
• Weber County’s estimated 2015 population of 242,737 is expected to grow to 330,732 by 2040, up 36.3%, and to 389,334 by 2065, up 60.4%.
• Salt Lake County’s estimated 2015 population of 1.09 million is expected to grow to 1.41 million by 2040, up 29.3%, and to 1.69 million by 2065, up 54.7%.

The anticipated growth rate in Washington County in Utah’s southwestern corner is expected to be even more dramatic, though the starting population base is smaller. The county’s estimated 2015 population of 154,602 is expected to grow to 320,956 by 2040, up 107.6%, and to 508,952 by 2065, up 229.2% in the 50 years.

Washington and Utah counties “are growing so fast right now,” said Harris.

Parsing the numbers, Harris said one notable difference figuring in the expected growth between Utah County and the rest of the Wasatch Front is the younger population. The younger the median age, the higher the birth rate, generally speaking. The estimated median age in Utah County as of 2019 was 25.9 years old, according to Kem C. Gardner Policy Institute figures. That compares to 32 years old in Davis County, 33.6 in Weber County, 33.8 in Salt Lake County and 37.9 in Washington County.

The 7.7-year median age difference between Utah and Weber counties may not seem like a lot, but “it actually is,” Harris said. Figuring in the young population in Utah County is the presence of two large universities, Brigham Young University and Utah Valley University. She also cited the presence of The Church of Jesus Christ of Latter-day Saints’ Missionary Training Center in Provo.

As Utah County’s economy diversifies and grows, resulting in more jobs, that too drives population increases. “That’s definitely a big part of it,” Harris said, noting the emergence and expansion of Utah County’s tech industry.

Then there are less tangible things, like the growth of the non-LDS population in Salt Lake County relative to the LDS population there. A 2018 story in the Salt Lake Tribune reported the LDS share of the population in Salt Lake County had dipped to 48.9%, less than half, the lowest figure since at least the 1930s. At the same time, members of the LDS Church in Utah County accounted for 82.2% of the population, and that sort of disparity, Harris said, could prod some LDS members to leave Salt Lake County for Utah County.

Likewise, the vastness of Utah County compared to geographically smaller Salt Lake, Davis and Weber counties helps with expansion. “I think right now there’s a lot of room to grow in Utah County,” Harris said.

Of course, just because Utah County’s current and expected growth overshadows the rest of the Wasatch Front doesn’t mean growth in Weber, Davis and Salt Lake counties is anything to look down on. In fact, boosters in Weber and Davis counties have bolstered efforts to promote the Northern Utah area to encourage business growth, thereby creating jobs and encouraging population growth.

“Weber has always been a little different, done it’s own thing,” Harris said, alluding to the local economic base in Weber County that provides many in the county with work.

Further south in Washington County, a completely different set of factors seems to figure in anticipated growth there.

The county has a solid base of retirees, Harris said, which has bolstered the health care industry there, creating a source of work for younger people. It’s closer geographically to California than the Wasatch Front, luring many Californians seeking a new home, and the Washington County area has a pair of national parks and other outdoor draws that bring in a lot of people.

Local officials are “starting to build their local economy and people are moving there,” Harris said.