What Accounts for Obamacare Numbers?

Yesterday's Congressional Budget Office report contained more than just a revision of its projections for Obamacare's effect on employment; it also revised the expectations for the controversial "risk corridor" plan, which basically taxes health insurers that make a lot more money than expected in the market and gives money to insurers who have bigger losses.

You might think from that description that this means it's budget-neutral: Insurers pay in, insurers take out. But that isn't the case; neither the pay-ins nor the pay-outs are capped. So, in theory, the government could transfer a bunch of money to insurers if the insurance market ends up with fewer young healthy customers than expected -- or, conversely, that the government could end up making money off the program.