The parameter ?_dos captures any partial correlation between tuition rates and homeownership among the control group, absorbing any state-level shocks that affect both tuition and the homeownership rate. Note that in specifications with state-by-year fixed effects ?₂ is not identified, as the average tuition rate is collinear with the fixed effects. The parameter ?_{step three} captures the average difference in homeownership rates between the treatment and control groups. We are left identifying ?_{step step 1}, the effect of student loan debt on homeownership, by the widening or shrinking of the gap in homeownership rates between public 4-year school attendees and the general population as tuition rates change, analogous to a difference-in-differences estimator. Read the rest of this entry »