why does g s maddala use limited dependent? why is $sigma_2u>sigma_1u$ why is the variable $aigma_2u$ being fulfilled why is sigma_2u why is sigma_e1u a limited dependent variable what does g s maddala think about variable constraints for econ why is sigma_2u in roy model why is $_2usigma_1u$ why is $sigma_1u why is $sigma_2u' a variable what model is used to find limited dependent variables in econometrics? why is sqligma variable used in roy model why is $sigma_2u>sigma_1u>$ fulfilled why is $sigma_2u oblong why is $sigma_1u$ a limited variable? why is $sigma_2u>sigma_1u> why is $sigma_ua valid in roy model why does the variable sigma why is $sigma_2u in roy models why is $sigma_2u>sigma_1u$ fulfilled