Thanks for the link, CarnalK. The Weiss study is not something an insurance regulator or company actuary would pay attention to. Here’s why.
The fundamental assumption in ratemaking is that the amount premiums is a function of the amount of claims. Here’s an example to illustrate the principle. The per cents are fairly typical:
Suppose Expenses are 30% of premiums
Desired Profit is 5% of premiums
Investment income is 45% of premiums
For every $100 of premiums, the insurance company will get an additional $45 of investment income, so total income is $145.
The company uses $35 for expenses and profit, leaving $110 for losses.
Now, turn it around and start with the loss estimate. Suppose the company projects an average obstetrician will have losses of $100,000. The company will charge her a premium of $110,000.
So, the way all insurance professionals determine how a law change will impact premium is to estimate how it will impact losses. E.g., a 25% reduction in loss costs will mean a 25% reduction in premiums. This is fundamental to all actuarial work.
Proportionality doesn’t always apply in the short run. Ratemaking in malpractice is uncertain. Companies may undercharge for several years, then catch up suddenly. There’s a whole other area of study of why rates vary. I studied the question a 15 years ago when I was the featured speaker on a special actuarial meeting on the insurance cycle.
Despite the insurance cycly, in the long run, premiums are based on losses. If you look at successful casualty insurance companies over a period of time, their ratio of loss to premium is typically in the range of 110% - 120%.
The Weiss study doesn’t differntiate between the impact of the insurance cycle and the impact of the change in benefits. That’s no way to bring clarity.