Higher oil prices and lower inflation-adjusted wages are making for some unhappy consumers -- an ominous mix that could have troubling implications for the economy.

The University of Michigan's latest American Customer Satisfaction Index fell nearly 1 percent in the first three months of the year, the biggest quarterly drop since 1997 except for an even bigger decline the last three months of 2004.

Researchers say the steep decline in the index the past two quarters -- to 73, its lowest level in two years and below its inaugural rate of 74.8 in the summer of 1994 -- could portend a slip in consumer spending, the primary source of fuel for the nation's economy.

Growth in consumer spending, which accounts for more than two-thirds of the nation's gross domestic product, has tended to slow in the past whenever the consumer satisfaction index has fallen by 0.3 points or more.

In looking at various segments of the economy, the researchers found the airline industry overall maintained its customer satisfaction level in the first quarter at the same level as a year ago, despite the difficulties that sector has faced.

US Airways, which has laid off thousands of workers in Western Pennsylvania and cut routes as it struggles to survive, saw its rating fall 9 percent to 57, the biggest drop-off and the lowest level of the industry's seven largest airlines. By comparison, Southwest Airlines, which just started flying out of Pittsburgh International Airport, had a 1 percent increase in its customer satisfaction rating and an overall rating of 74, the industry's highest and well above the average score of 66.

As a whole, fast-food restaurants improved their customer satisfaction score with Taco Bell and Burger King posting the biggest increases. The highest score went to pizza maker Papa John's International.

Patient satisfaction with hospitals fell 7 percent, on the heels of a 4 percent gain last year. The University of Michigan report cited rising costs of health care services plus reduced employer contributions that have forced consumers to pay a bigger portion of the bill as factors in the decline.

The overall satisfaction index is calculated quarterly but the researchers look at different segments at various times during the year. This quarter's index update included transportation, information, utilities, health care and accommodation and food services.