As Tim Jost points out today in the NEJM, the Ryan Plan also includes an individual mandate:
Fifth, both plans penalize Americans who choose to remain outside the insurance market, undermining the risk pool. The “individual mandate,” which imposes a tax penalty on Americans who can afford health insurance but choose not to buy it, is one of the most controversial provisions of the ACA. The Republican tax credit, however, is offered only to Americans who purchase health insurance. An incentive available only to those who comply with a condition is the exact economic equivalent of a penalty imposed for noncompliance with the same condition. Indeed, the price of remaining uninsured imposed by the Roadmap will in most instances be greater than that under the ACA.
Read the full article – simply the best evenhanded comparison of ACA v. Ryan that I’ve seen to date.