Part of the problem is that online purchases are increasing, and often escape sales tax (although online retailer Amazon recently agreed to collect Utah tax). Also, less of what people spend money on is now taxable, from education to health care. Even the sales tax on food has been reduced.
So Tennert said that in 1985, about 51 percent of household expenditures in Utah were subject to sales tax. By 2015, that had dropped to 41 percent.
Amid that, UTA President and CEO Jerry Benson said a few weeks ago that his agency cannot afford all the TRAX extensions, new bus rapid transit routes and additional streetcar systems now in long-term regional transportation plans unless residents approve a big tax hike.
He said long-range plans assumed transit sales tax would now be at a penny per dollar in purchases. It is far less. It is 0.69 of a cent per dollar in Salt Lake County. Raising it to a full penny per dollar would require a 45 percent sales tax boost.
But voters are unlikely to approve a tax hike until UTA can improve its image after scandals over high pay and sweetheart deals with developers, and an ongoing federal probe that now requires a federal overseer for UTA operations for three years.
The academy invited several officials to discuss how to improve the agency's image, and whether more transit truly will be needed as the population doubles.
"Perception is reality," warned Sen. Karen Mayne, D-West Valley City, saying UTA still has much work to convince residents it is trustworthy. One step, she suggested, would be to focus on improving some basics, such as neighborhood bus service.
"Buses aren't cute, and they're not flashy like FrontRunner, and they're not really cool like TRAX trains. But they're important to get people where they need to be," she said. Heavy borrowing in recent years to expand rail lines instead now has UTA spending more each year on debt service than on bus service.
Senate President Wayne Niederhauser, R-Sandy, said, "I tell you right now the tax infrastructure and revenue we have today is not sufficient to meet the demands of our growth. It just is not there in education, in transportation, in transit."
He said incremental tax increases that will be required would be smaller if they start sooner. But support for transit tax hikes may be complicated, he said, because most lawmakers and the public do not realize reforms that UTA has made in recent years.
"I'm hoping that these changes that have been made will make the difference" in improving public support as the agency and others explain them, Niederhauser said.
Carlos Braceras, executive director of the Utah Department of Transportation, warned that while the population here will double, because of geographic constraints, "We are not going to double the lane miles" of freeways and highways.
Some joked it would require double-decking Interstate 15.
"I just don't see a physical way to add more roads," said Rep. Mike Schultz, R-Hooper, chairman of the House Transportation Committee. "I don't think we're going to be doubling the size of I-15, so we need to be looking at other ways that's where transit falls into place."
Niederhauser said public officials have a big job ahead to convince the public that more transit is needed to handle growth.
"In order for these changes to be made, people have to accept those. I can advocate for those all day long, but if people in my district don't believe in them, then they are going to elect somebody else," he said. "I believe this is an educational issue."