As you know, McKinsey and Company is still refusing to release basic information about the methodology of its much-discussed study finding that large numbers of employers plan to drop insurance for workers after 2014, thanks to the Affordable Care Act.

Here’s something that makes this stonewalling appear even more suspect: Avalere Health, an independent, nonpartisan advisory firm, has now published what may be the most comprehensive look yet at all the research out there on this topic, and it shows in the clearest terms yet that McKinsey’s findings constitute a major outlier.

McKinsey's conclusion was that 30 percent of employers will definitely or probably stop offering employer-sponsored insurance after 2014. This has been widely repeated by Republicans and conservatives, even though other studies have found minimal impact and we have no way of evaluating the integrity of the research that produced McKinsey’s conclusion.

Now Avalere’s study of virtually all the research out there flatly contradicts this finding. It concludes: “Overall, our analysis suggests that the ESI market will be fairly stable after 2014 when key ACA coverage provisions go into effect.”

Click through the link for Avalere’s details and methodology, but the key thing to understand here is that this study by Avalere is unlike all the others. It’s the equivalent of a “poll of polls.” Avalere didn’t do its own survey. Rather, it attempted to evaluate the validity of many of the studies that have already been published. To supplement this, Avalere also talked to employer benefits consultants — that is, people who are in the business of helping employers make decisions about how to cover their employees — to get a closer view of the situation.

Bonnie Washington, a senior vice president at Avalere, tells me that the firm concluded that the studies finding that the ACA would have minimal impact on ESI are credible. “Most consultants are predicting fairly stable coverage after 2014,” she says.

Avalere’s study also flatly discounts the recent finding by Republican economist Douglas Holz-Eakin’s that many employers will drop ESI, finding his methodology wanting.

Here’s the kicker: Avalere didn’t even try to evaluate McKinsey’s study as part of this new effort — because McKinsey didn’t make enough info available about the study to make this possible.

“Without a better understanding of what their survey looked like and what assumptions they made, we don’t have enough information to evaluate their results,” Washington said.

It’ll be interesting to see if this latest study gets a fraction of the media attention lavished on McKinsey’s effort.