In a 2002 speech, Mark McClellan, a member of the Council of Economic Advisors at the White House, said that "[I]n the president's vision, all Americans should have access to high-quality and affordable healthcare." However, many healthcare researchers believe that a growing number of Americans are underinsured. Because any characterization of underinsurance will refer to the value judgments of people about what counts as "adequate" and "inadequate" healthcare, the goal of characterizing and measuring the underinsured is difficult to achieve. In (...) this article, I examine the various dimensions of underinsurance, and propose a typology incorporating those dimensions. (shrink)