I'm sure activity rates in Utah county, and even Salt Lake County, are higher than in the rest of the country and world - but I'd still be interested in knowing how many of that 85% are actually attending services.
I wouldn't be so sure. I met many, MANY Jack-Mormons-on-paper-only during my years living in Utah, who have no problem living in the belly of the beast, but also have not darkened the doorstep of their neighborhood LDS meetinghouse in years.
"On the rolls vs. in the pews • Martinich notes there's a big difference between being on the rolls and being a participating Mormon. He estimates that 40 percent of U.S. Mormons are active, and he has slightly different estimates for Salt Lake County. His best guess is that roughly half Salt Lake County's members are churchgoers, which would be 25 percent of the county's population. He says Utah County's activity rate is higher, so maybe 60 percent of its residents regularly attend worship services"
Estimates only, of course. TSCC won't release actual numbers. Personally, I find those estimates to be believable,
My parents lived in Utah county, and they had only one inactive family in their neighborhood. Their boys were thought to be thieves. You don't want to be inactive there, let alone non Mormon.