Will the health care exchanges lower prices over time?

Here are some interesting arguments from David Goldhill, here is one of them:

The designers of the health-care exchanges have also assumed that consumers, by shopping for the best deal, will drive down premiums. However, a major flaw in the design of insurance subsidies will insulate almost all of the initial customers — the estimated 20 million subsidized households — from concern about how much their policies cost.

Now, it’s not supposed to work this way. Only those Americans who don’t get insurance at work and who have income that puts them between 100 percent (138 percent in Medicaid expansion states) and 400 percent of the federal poverty level are eligible for exchange subsidies. As income rises within this bracket, the subsidy shrinks. But in practical terms, everyone who is subsidized has an infinite subsidy that will make them insensitive to premium levels.

How can that be? Let’s take an example. A family of four at 138 percent of the poverty level ($32,499) has its premium capped at 3.29 percent of income or $1,071. The rest is subsidy. So, if the cost of a silver plan is $10,000, the subsidy for this family is $8,929. A family at 400 percent of the poverty level ($94,200) has to pay up to 9.5 percent of its income for a plan, or $8,949. So the same $10,000 premium carries a subsidy of only $1,051.

…But now look at those two families from the insurer’s perspective. A $10,000 plan already costs more than the maximum amount either family would pay. If the insurer raises the premium to $10,001, both families get $1 in additional subsidy. If it raises premiums to $11,000, both families get $1,000 in additional subsidy. In other words, no matter how much an insurer raises rates, a subsidized household pays zero more.

The full piece is here.  Reihan adds useful comments.  This evidence does indicate that more sellers does lead to lower premiums, relative to fewer sellers.