RAS Technique

Definition

RAS Technique or RAS Procedure or RAS algorithm or biproportional matrix balancing technique is an algorithm originally introduced to update IO-tables in situations in which only limited survey data are available for the projection year.

The method is used in the preparation of updated I-O accounts that are based on partial survey information. The technique applies row and column balancing factors iteratively until the adjusted matrix (the transactions table) satisfies the row and column totals (commodity and industry output). The technique converges to a solution resulting in a balanced I-O matrix.

Procedure

The general form of the procedure is as follows:

$A^{'} = R A S$

where

• $A^{'}$ is a matrix of corrected input coefficients
• A is the matrix of input coefficients in base year
• R is a diagonal matrix of multipliers for rows
• S is a diagonal matrix of multipliers for columns

Assume that an input-output direct coefficients table for an n-sector economy for a given year in the past (designate this as year “0”) and that we like to update those coefficients to a more recent year (which we will designate year “1”).

The RAS technique generates an estimate of these coefficients from 3 n pieces of information for the year of interest (year 1).

• total gross outputs, $x_j$
• total interindustry sales by sector