The full-detail Social Accounting Matrix (SAM) gives a complete picture of the flow of funds, both market and non-market, throughout the economy in a given year. Market flows occur between the producers of goods and services (both industrial and institutional) and the purchasers of those goods and services, both industrial and institutional (i.e., households, government, investment, and trade). Non-market flows occur between institutions (e.g., between households and government, between households and capital, etc.) and are often called inter-institutional transfers. In such transactions there is no well-defined market value being exchanged in return for the payment; for example, while taxes are used to fund government services, these government services do not have a market value since they are not purchased in a market setting. In a typical SAM, the columns represent payments or expenditures by the column industry, commodity, or institution, while the rows represent a receipt of income by the industry, commodity, or institution.
National SAM
The column and row controls for nearly all elements of the U.S. SAM come from the BEA's National Income and Product Accounts (NIPA). Interior cell estimates come from our annual data development processes, with the exception of some elements of the institutional trade and capital accounts, which are calculated as part of the balancing routine. Balancing refers to the act of forcing each row sum to equal its corresponding column sum; balancing is necessary due to varying levels of precision and resulting rounding discrepancies in the data used to construct the SAM.
Sub-National SAM Data
With the exception of some inter-institutional transfers, the majority of the state, county, and zip code SAM data come directly from the regional IMPLAN industry data estimated as described here. The software allocates the remaining national SAM data to states, counties, and zip codes based on our IMPLAN industry data and other regional data. The software then combines these data with the industry data and balances the institutional trade and capital accounts to form a balanced regional SAM.
Household Transfers
Estimates of household income and transfer payments come from several sources, including the following:
- IMPLAN industry data (estimated as described here)
- REA tables CA35 (personal current transfer receipts) and SA50 (personal current taxes)
- NIPA Personal Consumption Expenditures (PCE)
- BLS Consumer Expenditure Survey (CES)
- The Annual Survey of State and Local Government Finances
- The Census Bureau’s State Government Tax Collections series
- The Census Bureau's Journey-To-Work data
Labor income received from industries is provided by IMPLAN industry data and is place-of-work income. Household income data, by contrast, are place-of-residence. The REA data include a residency adjustment, as well as some transfer payments data.
Household personal consumption expenditures are derived from the NIPA PCE data, with household income category detail obtained from the CES data. The national data are distributed to states and counties on the basis of the area's total household spending in each household income category. It is assumed that within a given income group, taxation and spending patterns are similar across the nation. While the CES data are available for 6 regions, analysis by IMPLAN did not show statistically significant differences in expenditure patterns across regions for a given household income category.
Taxes are regionalized to states and counties based on tax collection totals from the Annual Survey of Government Finances and the Census Bureau’s State Government Tax Collections series.
Government Transfers
The BEA NIPA datasets provide the control totals for government transfers. These control totals are allocated to states and counties based on IMPLAN industry data as well as data from the Annual Survey of State and Local Government Finances and the Census Bureau’s annual State Government Tax Collections series.
Enterprise
Enterprise is distributed based on estimated output for the region.
Capital
Payments by capital to other institutions represent net borrowing of money by that institution. Payments by other institutions to capital represent net savings by that institution. The capital accounts are a balancing item that is allowed to float. If the other elements are specified correctly, the capital accounts will be accurate.
Inventory
Inventory change is distributed based on estimated output for the region.
Trade
Payments by trade to other institutions represent a flow of money into the region from outside. Payments by other institutions to trade represent a flow of money from the region to other regions. Domestic imports and exports of commodities are specified as described here. Trade flows of labor income (i.e., commuter flows) are captured by Census Journey-To-Work data. The remainder of the trade entries are used for balancing.
Please see this article for more details on the structure of the IMPLAN SAM.