sambal.gms : Social Accounting Matrix Balancing Problem

**Description**

A Social Accounting Matrix captures all the circular flows in an economy and is called balanced if the row total equal the column totals. A sample problem illustrates the use of Nonlinear Programming to balance such matrices.

**Reference**

- Zenios, S A, Drud, A S, and Mulvey, J, Balancing some large Social Accounting Matrices with Nonlinear Programming. Tech. rep., Department of Civil Engineering, Princeton University, 1986.

**Small Model of Type :** NLP

**Category :** GAMS Model library

**Main file :** sambal.gms

$Title Social Accounting Matrix Balancing Problem (SAMBAL,SEQ=77) $Ontext A Social Accounting Matrix captures all the circular flows in an economy and is called balanced if the row total equal the column totals. A sample problem illustrates the use of Nonlinear Programming to balance such matrices. Zenios, S A, Drud, A S, and Mulvey, J, Balancing some large Social Accounting Matrices with Nonlinear Programming. Tech. rep., Department of Civil Engineering, Princeton University, 1986. $Offtext Set i accounts / lab, h1, h2, p1, p2 / ; alias (i,j); Table xb(i,j) original estimate lab h1 h2 p1 p2 lab 15 3 130 80 h1 na h2 na p1 15 130 20 p2 25 40 55 Parameter tb(i) original totals / lab 220, (h1,h2) na, p1 190, p2 105 / tw(i) wights for totals xw(i,j) weights for cells; tw(i) = 1; tw(i)$(mapval(tb(i)) eq mapval(na)) = 0; xw(i,j) = 1$xb(i,j); xw(i,j)$(mapval(xb(i,j)) eq mapval(na)) = 0; Display tw, xw; Variables x(i,j) estimated cells t(i) estimated totals dev deviations; Equations rbal(i) row balance cbal(j) column balance devsqr definition of square deviations; rbal(i).. t(i) =e= sum(j$xb(i,j), x(i,j)); cbal(j).. t(j) =e= sum(i$xb(i,j), x(i,j)); devsqr.. dev =e= sum((i,j)$xw(i,j), xw(i,j)*sqr(xb(i,j) - x(i,j))/xb(i,j)) + sum(i$tw(i), tw(i)*sqr(tb(i) - t(i))/tb(i)); Model bal / all /; x.l(i,j) = xb(i,j)$xw(i,j); t.l(i) = tb(i)$tw(i); Solve bal using nlp minimizing dev;