Finally, CEAs themselves have important limitations. Deciding where to draw the line between “high value” and “low value” remains controversial. Therefore, implementing the results of CEAs will probably involve comparison with a “band” within which interpretations are ambiguous (for example, $50 000 to $100 000 per quality-adjusted life-year) rather than with a single threshold (for example, $50 000 per quality-adjusted life-year). Cost-effectiveness analyses consider only the magnitude of health benefits and not their distributions, and equity considerations may sometimes supersede efficiency. In addition, CEAs remain highly dependent on analysts' underlying assumptions, evidence sources, and methods of sensitivity analysis. Although techniques are being developed to increase the transparency of these assumptions and their consequences (20), basing policy decisions on at least 2 analyses that are conducted independently and are shielded from conflicts of interest will probably remain prudent. However, although CEA methods are imperfect, to “make the perfect the enemy of the good” would be a mistake. Cost-effectiveness analysis is arguably the best way to compare the value of health care services on a level playing field by using an explicit, systematic, and quantitative method, and it is therefore the best candidate to link cost sharing to value.