While only 24 percent of people purchasing health insurance through the federal exchange are between the age of 18 and 34 (which is 14 percentage points lower than what the law needs to keep premiums low), The Washington Post's Ezra Kkein reports that younger, healthier people tend to sign up only when the penalty is about to hit. This enrollment behavior happened when Massachusetts rolled out its state insurance exchange. " Obamacare's enrollment pattern looks a whole lot more like Massachusetts than I would've thought given the disastrous launch and the challenging political environment," Klein blogs. Open enrollment ends April 1.