The creation and empirical use of economic freedom indices has produced a growing amount of literature over the last decade. A survey of this literature is provided, and the difficulty of measuring this concept, as well as the usefulness and limits of the various indices are discussed. The indices are reduced to their components, and testable models are used in order to determine which components are most important. Secure property rights are found to be the most important component driving the results. The results are consistent with previous studies, which indicate that greater economic freedom is related to greater growth and wealth. Not all of the components of an aggregate index have the same impact or even the same relationship. The aggregate indices are highly correlated at the international levels, lending support to the reliability of the measures, but there is no consensus on the appropriate aggregation method. Care should be put on the interpretation of the actual point estimates when the aggregate index is used empirically, but the relationships are robust and the indices are very useful and growing in importance.