Hi everyone!
I am using a model where I have an element: vector of state-level characteristics
I know how to do the vector, the problem is I don't know what variable to include in the vector? I am thinking population .. etc and what else ?\

I searched most papers and they don't actually specify which variables used in this vector. I am measuring the effect of Medicaid expansion on labor supply ( state level )
so what do you recommend?

Thanks !