JACKSON, Wyo. (AP) — The cost of staying in some of Yellowstone National Park's most historic lodges increased by up to a third this summer under a new, pilot pricing system that allows the lodging concessionaire more leeway in setting room rates.

But the change has drawn criticism that some people might be priced out of a stay in the nation's first national park.

In recent years, Yellowstone hotel rates have been set using a comparability analysis that aligns costs with those at similar hotels in gateway communities like Jackson, Cody and Gardiner, Montana.

But this summer park managers adopted a newly authorized National Park Service pricing system that applies to park concessionaire Xanterra's room rates.

"We're trying to balance access, as well as our need to be less bureaucratic and more efficient," Yellowstone business chief Zach Allely said. "In addition to that we're trying to make sure we remain affordable."

Using the new approach, Yellowstone is divvying its hotels into "core" and "non-core" facilities under what's being called a pilot project.

Core lodges tend to be those that are newer and have reasonable equivalents outside the park, and they'll continue to be governed by the old comparability price-control system.

The non-core hotels Xanterra has been given more control over include the Old Faithful Inn, the Lake Hotel and all of the Canyon lodging. Collectively, those account for about half of the approximately 2,300 rooms that Xanterra manages in Yellowstone. Rooms that fall into the non-core category are often historic and have no fair comparison outside the park.

"It's very difficult for us to come back and say to a concessionaire, 'This room that has a window view of the Old Faithful Geyser is the same as a room that has a window view of the street in Cody,'" Allely said.

However, any price increases cannot exceed 33 percent higher, Allely said.

In addition, he said, "If we find that the concessionaires, in our judgment, are abusing this privilege, then we have the authority to reel them back or to cancel the pilot altogether."

It's unclear exactly how much Xanterra has taken advantage of its new wiggle room in setting prices, the Jackson Hole News & Guide reported .

Xanterra's Yellowstone concessions program manager, Mike Heller, said there were times this spring when rates were actually less than last year. Costs more recently might be 8, 15 or 25 percent above 2017 rates on any given day, he said.

"Because it's market-based pricing it varies on a day-by-day basis," Heller said.

Compared with last year, rates at one of Yellowstone's flagship lodges, the Lake Hotel, were up between 20 and 25 percent for a stay on Friday. A year ago a room on the hotel's backside cost $379, but was going for $456 as of Monday afternoon. A room with a view of Yellowstone Lake the same day was $399 in 2017; on Friday it was priced at $506.

The increases drew scorn from frequent Yellowstone visitor Ken Barrick, a Fairbanks, Alaska, resident and retired university professor who decried the changes in a June 27 News & Guide opinion piece.

"Do the math: If an American family plans a weeklong vacation in Yellowstone, they will pay hundreds of dollars more for a room at the best hotels," Barrick wrote. "Many Americans will simply be priced out of an overnight stay."

Yellowstone's Allely and Xanterra's Heller said they remain committed to accommodating guests of lesser financial means.

Heller said half of Yellowstone's lodging is still subject to the stricter price controls, and prices for those units frequently fall below market rates elsewhere in the region.

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