Doctors in the United States are sued five times more often than those in Canada, researchers reported Thursday.

They said the Canadian legal system discourages frivolous lawsuits, while the United States encourages the payment of small settlements in many cases that would not be brought in Canada or would be decided in the doctor's favor.As a result of these and other differences, Canadian doctors' malpractice insurance rates are only about one-ninth those of American doctors.

The analysis, conducted by Peter C. Coyte and others from the University of Toronto, was published in the New England Journal of Medicine.