摘要
We can make a useful distinction between theoretical and applied econometrics. The-orists develop new techniques for estimation and hypothesis testing and analyze theconsequences of applying particular methods when the assumptions that justify thosemethods are not met. Applied econometricians are the users of these techniques andthe analysts of data （"real world" and simulated）. Of course, the distinction is farfrom clean; practitioners routinely develop new analytical tools for the purposes ofthe study that they are involved in. This book contains a large amount of economet-ric theory, but it is directed toward applied econometrics. I have attempted to surveytechniques, admittedly some quite elaborate and intricate, that have seen wide use "inthe field."
Another useful distinction can be made between microeconometrics and macro-econometrics. The former is characterized largely by its analysis of cross section andpanel data and by its focus on individual consumers, firms, and micro-level decisionmakers. Macroeconometrics is generally involved in the analysis of time-series data,usually of broad aggregates such as price levels, the money supply, exchange rates,output, investment, and so on. Once again, the boundaries are not sharp. The very largefield of financial econometrics is concerned with long time-series data and occasionallyvast panel data sets, but with a very focused orientation toward models of individualbehavior. The analysis of market returns and exchange rate behavior is neither macro-nor microeconometric, or perhaps it is some of both. Another application that we willexamine in this text concerns spending patterns of municipalities, which, again, restssomewhere between the two fields.
Applied econometric methods will be used for estimation of important quantities,analysis of economic outcomes, markets or individual behavior, testing theories, and forforecasting. The last of these is an art and science in itself, and （fortunately） the subjectof a vast library of sources. Although we will briefly discuss some aspects of forecasting,our interest in this text will be on estimation and analysis of models. The presentation,where there is a distinction to be made, will contain a blend of microeconometric andmacroeconometric techniques and app
ications. The first 11 chapters of the book arelargely devoted to results that form the platform of both areas. Chapters 12 to 13 focuson time series modeling while Chapters 14 to 15 are devoted to methods more suitedto cross sections and panels, and methods used more frequently in microeconometrics.We will not be spending any time on financial econometrics. For those with an interestin this field, I would recommend the celebrated work by Campbell, Lo, and Mackinlay（1997） and, for a more time-series-oriented approach, Tsay （2005）. It is also necessaryto distinguish between time-series analysis （which is not our focus） and methods thatprimarily use time-series data. The former is, like forecasting, a growth industry servedby its own literature in many fields. While we will employ some of the techniques oftime-series analysis, we will spend relatively little time developing first principles.
The techniques used in econometrics have been employed in a widening vari-ety of fields, including political methodology, sociology [see, e.g., Long （1997） andDeMaris （2004）], health economics, medical research （how do we handle attrition frommedical treatment studies？） environmental economics, transportation engineering, andnumerous others. Practitioners in these fields and many more are all heavy users of thetechniques described in this text.
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