Widespread upgrades and new amenities didn't stop the hotel industry from slipping from a year ago in the University of Michigan's American Customer Satisfaction Index.

The hotel industry scored 71 out of 100, down from 75 last year, according to the survey, which is compiled annually and based on responses from 80,000 U.S. consumers queried about a broad range of their recent dealings with businesses. Tepid scores for budget and midprice hotels caused the decline.

As an industry, hotels have been pumping billions into upgrades, a reflection of strong demand and healthy profits over the last three years.

Four large hotel companies in the United States — Marriott, Hyatt, Hilton and Starwood — scored well above the industry average, showing that efforts to upgrade may be paying off.

A group of budget and midprice hotels labeled "others" by the study had the deepest drop from 2006. The category, which study officials say includes chains such as Days Inn, Best Western and Red Roof, scored 70, down 6 points from a year ago.

Joe McInerney, CEO of the American Hotel & Lodging Association, said those chains rely entirely on franchisees to run their properties.

As a result, they have less control over the quality of customer service, McInerney says.

Business traveler Patrick O'Toole of Burnsville, Minn., says he has noticed service slipping in midprice hotels. "I certainly expect it to be lower quality than the full-service hotels, but it frequently falls below my already-low expectation level," he says.

Among the biggest companies, only Hilton, down 2 points from 2006, saw a decline. Customers felt they were getting "less bang for their buck" at Hilton's chains, says David VanAmburg, an ACSI official.

Ernie Wooden, a brand executive at Hilton, said its internal survey shows that its customer-satisfaction level has improved this year for the Hilton brand and increasing market share shows customers "are giving us more than a fair share of the business."