xtabond2 lnSWG lnGSDP lnGSDP_SQ SWG_L1 Health_Exp TotExp_ULB Urban_rate lnPopdens Pol_Stability HDI Slum, gmm( > SWG_L1 lnGSDP lnGSDP_SQ, collapse) iv( Health_Exp TotExp_ULB Urban_rate Pol_Stability HDI Slum lnPopdens, equ > ation(level)) twostep robust orthogonal small nodiffsarga