An EST= input data set supplies the coefficients of the equation system. The data set containing the coefficients is normally a "TYPE=EST" data set created by the OUTEST= option of PROC SYSLIN or another regression procedure. The data set contains the special variables _TYPE_, _DEPVAR_, and INTERCEPT. You can also supply the structural coefficients of the system to PROC SIMLIN in a data set produced by a SAS DATA step as long as the data set is of the form TYPE=EST. Refer to SAS/STAT software documentation for a discussion of the special TYPE=EST type of SAS data set.
Suppose that there is a g  1 vector of endogenous variables y
1 vector of endogenous variables y  , an l
, an l  1 vector of lagged endogenous variables
1 vector of lagged endogenous variables  , and a k
 , and a k  1 vector of exogenous variables x
1 vector of exogenous variables x  , including the intercept. Then, there are g structural equations in the simultaneous system that can be written
, including the intercept. Then, there are g structural equations in the simultaneous system that can be written 
               
               
               
               
            
![\[ \mb{G} \mb{y} _{t}=\mb{C} \mb{y} ^{L}_{t}+\mb{B} \mb{x} _{t} \]](images/etsug_simlin0004.png)
where G is the matrix of coefficients of current period endogenous variables, C is the matrix of coefficients of lagged endogenous variables, and B is the matrix of coefficients of exogenous variables. G is assumed to be nonsingular.