Multisector vs single contribution analysis
Hi,
There have been lot of discussion regarding single sector vs multisector contribution analysis. Some use internal adjustment method (in IMPLAN software  changing commodity production and making RSC to zero) while some use matrix inversion method (using SAM matrix to create square matrix for sectors of interest, inverting it, and multiplying with output from study area data to get adjusted values). Results from both methods tend to differ slightly and its up to investigator objective to chose one.
My question here is, suppose we would like to do contribution analysis for sectors A, B, and C individually as well as a whole. Summing the total contributions reported by individual sector A, B, and C analysis will be higher than that of running multisector analysis (A, B, C, together) because by summing individual sector total contribution, some of the indirect and induced effect (say A) happens to be direct effect for other sector (say B or C). So there is some double counting.
While if we do internal adjustment for all sectors (A, B, and C) and do single sector analysis in the same model we will get the sum of individual sectors total contribution equal to multisector (A, B, C together) total contribution. But doing so, aren't we losing individual sector identity. Is it a good idea to run individual sector (say A) analysis in the same model where we did internal adjustment for A, B, and C to run multisector analysis?
Also, for matrix inversion, is it advisable to use same adjusted value that we derive from 3x3 matrix (SAMs for sector A, B and C) to shock the mode for single sector analysis?
I would like to report results for A, B, and C individually as well as a whole.
Thank you.

Yes, we would recommend modifying the model/spreadsheet so that no Industry or Institution buys anything that Industries A, B, and C produce. In this way, there is no doublecounting and sector detail is maintained, and a single matrix can be used.
Using the "adjusted output value" approach to Industry Contribution Analysis only works for singleindustry contribution analysis (and also restricts the industry to only be allowed to produce one commodity, as a side note).
We encourage you to try the new online platform at app.implan.com, as it does all of this for you automatically when you select the Industry Contribution Analysis type. There is great information on our support site for Industry Contribution Analysis.
Thanks!
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