The federal government has released enrollment figures for the Affordable Care Act (ACA, aka Obamacare) Marketplaces from inception on Oct. 1 through Dec. 28, pegging overall sign-ups at "nearly 2.2 million." The figure covers both federal and state health insurance exchanges. (The report does not say how many have actually paid premiums.)

The goal is for 7 million enrollees by the end of March, with 40 percent of them coming from "young invincibles" aged 18 to 34, but so far only 24 percent of enrollees fall into that age group.

Young, healthy people are a key component of covering expenses for older, sicker individuals, as envisioned under the ACA, prompting speculation that a) the federal government will have to provide subsidies to the insurance companies this year and b) the insurance companies next year will have to increase the premiums they charge.

As the report itself notes: "There has been considerable interest in encouraging young adults to enroll in Marketplace plans because this age group is most likely to be without health insurance coverage; enrollment of young adults is also important to help to ensure a favorable risk mix."