The residual in an estimated equation is composed by measuring errors and omitted variables. If an omitted variable is autocorrelated it can to some degree be included in the model by the lagged autocorrelated residual. It can be shown that in a variable coefficient built after the principle of...

China?s open-door policy has attracted foreign investment to China. The foreign direct investment is unequally distributed in Chinese thirty regions. The regions can be grouped after different critiria: the coastal area, the central area and the western area by geographical critirion, or...