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SAM balancing methods and programs

The Modelling and Policy Impact Analysis (MPIA) program assists developing country researchers in constructing models of their national economy to simulate the impact of macroeconomic shocks/policies on various dimensions of poverty and welfare. To do so, it applies a combination of macro-micro modelling and simulation techniques including, for the macroeconomic level approach, a Computable General Equilibrium (CGE) framework. CGE models are usually built on the basis of data assembled in a Social Accounting Matrix (SAM), which needs to be balanced. On this page, modelers will find SAM-balancing tools which have been developed or adapted by PEP researchers.

SAMBAL is a simple computer program to balance a SAM. Computable general equilibrium modeling requires a consistent and coherent benchmark data set, usually organized in the form of a Social Accounting Matrix (SAM). These data generally come from quite diverse sources and correspond to different periods of time. As a result, they often present inconsistencies. SAMBAL makes it possible to reconcile this information in order to balance a SAM. The program minimizes the changes to the base data using one of two optimizing techniques, cross-entropy (the default) or least squares. The program is an attractive and easy alternative to the arbitrary and time-consuming manual and other haphazard methods sometimes used to balance SAMs.

GPCEMA stands for « General Purpose Cross-Entropy Matrix Adjustment ». The matrix adjustment program is based on the minimum information-gain principle (also known as minimum cross-entropy), as it has been extended to deal with negative entries by Junius and Oosterhaven (2003). In addition to handling standard matrix adjustment problems, the program automatically deals with situations where row sums, column sums, or both are constrained to zero. It is based on    
LEMELIN, André (2009), « A GRAS variant solving for minimum information loss », Economic Systems Research, 21(4), p. 399-408.

Related resources include :
Robinson, Sherman, Andrea Cattaneo, and Moataz El-Said. 2001. “Updating and Estimating a Social Accounting Matrix Using Cross Entropy Methods.” Economic Systems Research, Vol. 13, No. 1, pp. 47-64.    
    http://www.ifpri.org/publication/estimating-social-accounting-matrix-usi...
Robinson, Sherman. 2013. cesam2.gms : Cross Entropy SAM Estimation program: 
    http://www.gams.com/modlib/libhtml/cesam2.htm

Free public access under a Creative Commons license

The programs offered here are truly «open source»: free public access is available via the links below. Each program is fully documented and all the relevant files are freely accessible.

For detailed information, follow the links below:

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