The systematic study of the government of more than one country. One of the main subdivisions of the study of politics. Until recently, however, it was usually very unsystematic. Much of what passed for comparative government was simply the study of the government of a small number of large countries. A typical course or textbook would cover two or three parliamentary democracies and one or two communist regimes. While it is certainly useful for any student of politics to know something about the institutions of three or more countries, that is not comparative politics until it involves some comparisons.
What comparisons are useful? The oldest form of comparative government is the study of constitutions. The first known such work is Aristotle's compilation of the constitutions and practice of 158 Greek city‐states, of which only the Constitution of Athens survives. Undoubtedly, however, comparisons between different city‐states underpin some of the generalizations in Aristotle's Politics, just as comparisons between different living organisms underpin his biological writing.
Biology has made great strides since Aristotle; the comparative study of constitutions has not. This is partly because it is difficult to get the right level of generality. Some studies compare all the countries in the world. Some useful statistical generalizations can be made about them. But there is no scholarly agreement on such basic questions as the relationship between the economic development of a country and its level of democracy. Another approach is to look at all cases of a common phenomenon—such as revolutions, totalitarian states, or transitions to democracy. In some cases these are dogged by difficulties of definition. For instance, what is to count as a revolution?
The commonest form of comparative government remains the detailed study of some policy area in two or more countries. Sensitive researchers are always aware of the problem of ‘too few cases, too many variables’. Consider a popular research programme in the 1980s and 1990s: the impact of corporatism on gross national product. It is clearly not straightforward. Some corporatist and some anticorporatist countries have had fast economic growth; some corporatist and some anticorporatist countries have had slow economic growth. There can be many reasons why a country becomes corporatist, and many reasons why an economy grows fast (or not). No researcher, or even collaborative team, can hope to know enough about more than perhaps five countries to talk about each of their institutions in a well‐informed way. So they can never be sure whether the factors they identify as the causes of growth really are the true causes. In recent years, this literature has improved, with several large multiple‐regression‐based studies of all countries, all democracies, or all OECD countries.
These difficulties have always surrounded comparative government. Nevertheless, researchers are far more sensitive to the difficulties of generalization than they once were, and accordingly more tentative in their conclusions.