2. When estimating immigrant assimilation, we worry that we might overstate or understate true assimilation due to changing cohort quality and selective return migration. All else equal, if cohort quality is increasing over time then we will (understate overstate) assimilation looking at a single cross-section. All else equal, if the more skilled migrants return to their home country, we will (understate/overstate) assimilation using a single cross-section. (a) Understate; Understate (b) Understate; Overstate (c) Overstate; Understate (d) Overstate: Overstate