There are many cross-national measures of democracy (i.e. level of democracy) and they seem to compete with one another for the title of "best measure." Clearly, in general, measures are appropriate for some things, but not all things, and they depend on context. My question is about (a) the conceptual foundations of the various measures of democracy, (b) the methodology of the measure (expert opinions, use of mass surveys, and so on) and (c) the empirical associations between the measures. Who has compared the various measures, and what did they conclude?