 Contemporary economics is diverse. There are many schools and many branches. Even so-called “orthodox” or “mainstream” economics has many variants. Some mainstream economics is highly theoretical, though most of it is applied and relies on rudimentary theory. Theoretical and applied work can be distinguished as microeconomics or macroeconomics. There is also a third branch, econometrics which is devoted to the empirical estimation, elaboration, and to some extent testing of microeconomic and macroeconomic models (but see Summers 1991 and Hoover 1994).