The study also found that from 1997-to-2002, per-claimant medical expenses increased the most in Texas, compared with the other three states.

IRC's report, "Analysis of Auto Injury Insurance Claims In Four Tort States," examined detailed information from auto injury claims that closed with payment. The organization said the four states involved in the research have similar auto insurance regulations.

The study found that:

oIn California, 57 percent of injury claimants went to a chiropractor==compared with 28 percent in Illinois, 43 percent in Texas and 46 percent in Washington.
oMore than half (53 percent) of California injury claimants' medical fees came from chiropractors==compared with 26 percent in Illinois, and 44 percent in both Texas and Washington.

o In each of the four states, neck or back sprains were the most serious injury for at least seven in 10 bodily injury claimants and at least three-quarters suffered no disability from the accident.

oFrom 1997-to-2002, the average medical expenses claimed increased by 39 percent in Texas==compared with 25 percent in California, 24 percent in Illinois, and 9 percent in Washington. Over this same time period, medical cost inflation was 22 percent.

IRC said similar patterns emerged in first-party medical payments claims in California and Illinois, along with personal injury protection claims in Texas and Washington.

In all four states, average bodily injury payments exceeded claimed economic losses, reflecting auto insurance payments for general damages (sometimes referred to as pain and suffering), the study found.

Claimed economic losses in 2002, mainly consisting of medical expenses, were highest in Illinois and California bodily injury claims==averaging $5,506 and $5,409, respectively.

The corresponding average insurance payments to bodily injury claimants were $7,850 in Illinois and $7,830 in California. In comparison with these two states, Texas claimants averaged lower reported economic losses ($4,483) and injury payments ($5,768).

Washington injury claimants' economic losses averaged $3,833==the lowest of the four states. However, average bodily injury payments were $7,594 in Washington, which is near the levels in Illinois and California.

"Auto insurance claimants often seek different types of medical treatment for the same types of injuries, and this apparently varies by the state in which the accident occurs," explained Elizabeth Sprinkel, senior vice president of the IRC. "Regardless of treatment type, however, insurers' bodily injury payments exceeded claimed expenses on average in each of these four states."

Vicky Kilgore, an IRC researcher, said one factor in the different state expenditures is difference in coverage and policy limits.

For example, she noted differences in personal injury protection, first-party coverage between Texas and Washington. In Texas, the minimum amount of coverage is $2,500, compared with $10,000 in Washington.

In choosing a medical provider, she said a possible factor in choice patterns could be "cultural differences" among states as well as the availability and prevalence of certain types of practitioners.