Imbens, Guido; Hirano, Keisuke; Ridder, Geert; Rebin, … - National Bureau of Economic Research (NBER) - 1998
In many fields researchers wish to consider statistical models that allow for more complex relationships than can be inferred using only cross-sectional data. Panel or longitudinal data where the same units are observed repeatedly at different points in time can often provide the richer data...