The total cost per student of public colleges in the United States increased an average of 11 percent over the last year, but there were wide disparities in the costs among the states, according to a new Education Department study.

The 50-state survey released yesterday also reveals that, despite an increase in state appropriations, when inflation was taken into account the purchasing power of the appropriations fell over the last seven years. States are beginning to rely increasingly on tuition instead of state tax dollars to finance the skyrocketing costs of public higher education.

State appropriations counting inflation have declined an average 1.6 percent nationwide over the seven years, and tuition has increased an average 12.1 percent.

At the top of the per-pupil cost chart is Alaska, where it costs $11,683 for each public-university student. Second is the District of Columbia, at $8,933.

Maryland and Virginia fall in the lower end. Maryland's per-pupil cost is $4,327 and Virginia's is $4,291.

According to Kent Halstead, a reseacher and economist at the National Center for Education Statistics, which prepared the report, the increased average costs reflect universities' heightened concern over inadequate faculty salaries and an effort to catch up.

"Faculty salaries have generally not kept pace with inflation," he said. "They lost almost 20 percent in purchasing power since 1973." Even with the increases over the last year, he said, "they are still 16 percent behind in purchasing power" compared to 1973.

The variation among the states in per-pupil cost is "tremendous," Halstead said. Alaska is 2.75 times the national average. Oklahoma, by contrast, is 30 percent below the national average.

There is also wide disparity in how much revenue the states receive from tuition.

Tuition revenue per student was highest in Vermont, at $3,545. The reason is that so many out-of-state students attend its public colleges and pay a higher nonresident fee. California is lowest at $500 per student, because that state traditionally has kept tuition low for residents and nonresidents alike at its heavily subsidized public colleges.

The in-depth study also reveals how various states rank in attracting their own high school graduates to home-state public colleges.

The District of Columbia and Connecticut are the worst in this measure, for different reasons.

In the District, there are only 1.37 public-university students for each D.C. high school graduate -- but the District is small, and there is only one public university in the city, the University of the District of Columbia.

In Connecticut, there are 1.37 public-college students for each high school graduate. But Connecticut, with a wealth of private colleges, is "not really in the higher education business," the study says.