文件面板数据简介基于计量济学导论中章节.pdfVIP

INTRODUCTION to REGRESSION YSIS WITH PANEL DATA A panel data set, or longitudinal data set, is one where there are repeated observations on the same units. The units may be individuals, households, enterprises, countries, or any set of entities that remain stable through time. The National Longitudinal Survey of Youth is an example. The same respondents were interviewed every year from 1979 to 1994. S e 1994 they have been interviewed every two years. A balanced panel is one where every unit is surveyed in every time period. The NLSY is unbalanced because some individuals have not been interviewed in some years. Some could not be located, some refused, and a few have died. 4 REGRESSION YSIS WITH PANEL DATA: INTRODUCTION Panel data sets have several advantages over cross-section data sets: • They may make it possible to e a problem of bias caused by unobserved heterogeneity. • They make it possible to investigate dynamics without relying on retrospective questions that may yield data subject to measurement error. • They are often very large. If there are n units and T time periods, the potential number of observations is nT. • Because they tend to be expensive to undertake, they are often well designed and have high response rates. The NLSY is an example. 8 REGRESSION YSIS WITH PANEL DATA: INTRODUCTION k s Y = b +b X +g Z +dt +e it 1 j jit p pi it j =2 p =1 The starting point for a discussion of regression models using pa