MODEL:
! Downside risk portfolio model;
SETS:
    ASSET/ ATT GMC USX/ :
        INVEST;  ! Amount to invest in each asset;
    SCENARIO/1..7/:
        TRETRN,  ! Return under this scenario;
        DRISK;   ! Downside risk under this scenario;
    TABLE( SCENARIO, ASSET):
        ARETRN;  ! Return under scenario I of asset J;
 ENDSETS
 DATA:
! Desired return;
    DRETURN = .13;
! Threshold, below which we are unhappy;
    THRESH = .11;
! Power to use for risk(1 or 2);
!  When NPOW = 1, it is a linear program;
!  When NPOW = 2 and threshold = desired return;
!   it is the semi-variance;
    NPOW = 2;
    ARETRN =
    -.071  .144  .169
     .056  .107 -.035
     .038  .321  .133
     .089  .305  .732
     .090  .195  .021
     .083  .390  .131
     .035 -.072  .006;
 ENDDATA
! Minimize average downside risk;
    MIN =  @SUM( SCENARIO: DRISK ^ NPOW)/ 7;
! Compute return for each scenario;
    @FOR( SCENARIO( I):
     TRETRN( I) = @SUM( ASSET( J):
      ARETRN( I, J) * INVEST( J));
! .. and how much we fall short of threshold ;
     DRISK( I) >= THRESH - TRETRN( I);
! Return in a period could be negative;
     @FREE( TRETRN( I));
    );
! Our budget constraint(divided by a billion);
   [BUDGET] @SUM( ASSET: INVEST ) = 1;
! Our desired return;
   [PRICER] @SUM( SCENARIO( I): TRETRN( I))/ 7 >= DRETURN;
END