In recent years three different quantitative studies measuring the extent of regulation in OECD nations have appeared. One analysis is based on an extensive review and quantification of laws and regulations; the other two are based on opinion data of those familiar with these regulations. Despite their very different methodologies and coverage of particular types of governmental regulation, the results of the three studies are significantly correlated, even though they differ in detail. The advantages and disadvantages of each of the three approaches are discussed.