15.16 Using the data set from Exercise 15.15, consider the model Ln(PRODi,): 9r' * $2,1n(AREAi,*) 9r' ln(LABORi,) * F+rl n(FERTiT)- f e;,

(a) Estimate three seemingly unrelated regressions for the years 1995, 1996, and 1997 and report the results.

(b) What assumptions are you making when you estimate the equations in (a)? How would you interpret what was called contemporaneous correlation in Section 15.3? Is this correlation significant?

(c) Test the hypothesis that the input elasticities are the same in all 3 years.