** Chapter 12.3 ** for W.H. Greene, Econometric Analysis 6th ed. *****************
* (c) Noel Roy 2008
*
*				               INSTRUMENTAL VARIABLES ESTIMATION
*
*===============================================================================
* Example 12.3 Labor Supply Model (p. 320)
*
READ (TableF9-1.txt) /NAMES
*
* Estimate the labor supply equation using OLS.
OLS wks lwage ed union fem
*
* Specify the list of exogenous variables in the demand-supply model as
* z1 = [constant,ind ed union fem]. 
* The synax of the INST command is
* INST depvar rhsvars (exogvars) / options
* By default, the constant term is specificed as  exogenous.
INST wks lwage ed union fem (ind ed union fem)/DN
*
* Now add SMSA to the list of exogenous variables z2.
INST wks lwage ed union fem (ind ed union fem smsa)/DN
*
* Test whether lwage is exogenous using the Wu specification test (p. 324).
*
* Get the predicted values in a regression of lnwage on the first set
* of instrumental variables z1.
*
?OLS lwage ind ed union fem / PREDICT=lwghat
*
* Regress wks on the independent variables and lwghat.
*
OLS wks lwage ed union fem lwghat
*
* Test the null hypothesis that the coefficient of lwghat is zero.
*
TEST lwghat
STOP
*
*===============================================================================
* Updated October 20, 2008