Last Monday, Jed Graham of Investor's Business Daily reported that insurers say Patient Protection and Affordable Care Act enrollment is shrinking, and it is expected to shrink further. Some of those who signed up for insurance on the exchanges never paid; others paid, then stopped paying. Insurers are undoubtedly picking up some new customers who lost jobs or had another "qualifying life event" since open enrollment closed. But on net, they expect enrollment to shrink from their March numbers by a substantial amount — as much as 30 percent at Aetna Inc., for example.

How much does this matter? As Charles Gaba notes, this was not unexpected: Back in January, industry expert Bob Laszewski predicted an attrition rate of 10 to 20 percent, which seems roughly in line with what IBD is reporting. However, Gaba seems to imply that this makes the IBD report old news, barely worth talking about, and I think that's wrong, for multiple reasons.

The first is simply that we didn't know what the attrition rate would be until we actually saw the final numbers, and it could have been lower — or higher — than Laszewski suggested. It's always valuable to have actual data rather than guesstimates (and we should remember that we're still getting data; we won't know the final attrition rate until December).