The Nexus Project is a collaboration between IFPRI and its partners, including national statistical agencies and research institutions. Our aim is to improve the quality of social accounting matrices (SAMs) used for computable general equilibrium (CGE) modeling. The Nexus Project develops toolkits and establishes common data standards, procedures, and classification systems for constructing and updating national SAMs. This addresses the need for greater transparency and consistency in SAM construction to strengthen model-based research and policy analysis in developing countries. Nexus SAMs allow for more robust cross-country comparisons of national economic structure, especially agriculture-food systems. The Nexus Project’s guiding principles are that all data should be traceable to original sources and/or assumptions, and that all SAMs should be freely available online. Greater transparency and accessibility should facilitate more data validation and participation of the modeling community. Statistics are continuously being revised and errors are often only identified when data is used for analysis, and so we welcome your suggestions on how the SAMs can be improved to reflect new and/or better information.

The open access versions of Nexus SAMs separate domestic production into 42 activities. Factors are disaggregated into labor, agricultural land, and capital. Labor is further disaggregated across three education categories. The Nexus SAM defines household groups, namely rural and urban households disaggregated by per capita expenditure quintiles. The remaining accounts include enterprises, government, taxes, savings-and-investment, and the rest of the word.

Countries with Nexus SAMs

 

Nexus SAMs are constructed using a Nexus SAM Building Toolkit developed by IFPRI. During the first stage, a Macro SAM is constructed from and fully consistent with official National Accounts, Government Finance Statistics, and Balance of Payments data. During the second stage, income and expenditure shares derived from household surveys and other sources are used to disaggregate the Macro SAM across multiple activities, commodities, factors, and households. Account imbalances are corrected through cross-entropy estimation.

All Nexus SAMs are published on the IFPRI Dataverse, along with links to their respective data papers. For further information, please email: IFPRI-Nexus.

Nexus SAMs

Duration

2016- Ongoing

CGIAR Initiatives

Foresight

Donors/Funders

United States Agency for International Development (USAID)
Bill & Melinda Gates Foundation
CGIAR Research Program on Policies, Institutions, and Markets (PIM)
Links
COVID-19: MEASURING IMPACTS AND PRIORITIZING POLICIES FOR RECOVERY
RIAPA Models Project
AIDA Tool
LEAS Model

Outputs / Resources


View All Non Peer-Reviewed Publications


View All Datasets

Nexus SAMs represent the socioeconomic structure of an economy at a point in time. It captures resource flows associated with transactions and transfers between all economic agents. Nexus SAMs are the databases of choice for calibrating IFPRI’s single country, economywide models. SAM multiplier models are the simplest of these models. They can be used to measure the magnitude and nature of sectoral multiplier effects and to analyze distributional effects associated with an exogenous injection into the economy. SAM multiplier models assume relative prices are fixed and resources are unconstrained. This imposes some limitations as far as the type of simulations that can be conducted and the timeframe of an analysis. For more information on SAM multiplier models and exercise, see Breisinger et al. (2009).

CGE models, while calibrated to the same data, relax many of the restrictive behavioral assumptions of SAM multiplier models. These models also capture the linkages and market interactions between producers and consumers in an economy but incorporate more flexible behavioral features such as multi-level nested production functions, imperfect substitution between domestic and imported commodities, and a linear expenditure system of consumer demand. Economic agents respond to market prices which adjust to establish equilibrium in markets. Various closure rules define the market clearing mechanisms in the model. IFPRI maintains both static (Lofgren, Harris and Robinson 2002) and recursive-dynamic CGE models (Diao and Thurlow 2012).

Breisinger, C., M. Thomas, and J. Thurlow. 2009. "Social accounting matrices and multiplier analysis: An introduction with exercises." Food Security in Practice Technical Guide 5. Washington D.C.: International Food Policy Research Institute. https://www.ifpri.org/publication/social-accounting-matrices-and-multiplier-analysis.

Diao, X., and J. Thurlow. 2012. "A Recursive Dynamic Computable General Equilibrium Model." Chap. 2 in Strategies and Priorities for African Agriculture: Economywide Perspectives from Country Studies, by X. Diao, J. Thurlow, S. Benin and S. Fan, 17-50. Washington, DC: International Food Policy Research Institute (IFPRI). https://www.ifpri.org/publication/recursive-dynamic-computable-general-equilibrium-model.

Lofgren, H., R.L. Harris, and S. Robinson. 2002. A standard computable general equilibrium (CGE) model in GAMS. Microcomputers in Policy Research, Washington, DC: International Food Policy Research Institute. https://www.ifpri.org/publication/standard-computable-general-equilibrium-cge-model-gams-0.