Multi-Industry Contribution Seperating Sectors
When completing a Multi-Industry Contribution Analysis on 8 industries, we would also like to look at each of those 8 industries separately in further detail. Are there any issues with creating a new activity for each of the 8 industries after making the adjustments on the model following the multi-industry methodology? Doing this yields different results (lower in our case) than conducting a single industry contribution analysis as shown at the link below. Adopting the multi-industry approach for the 8 individual industries gets much closer (<1%) than using the single industry approach and comparing to the multi-industry approach for the 8 industries together. We want to be sure that the sum of the parts (8 industries) does not exceed the total aggregated industries. Thanks! Michelle
Hello, Is sounds like you are summing the 8 individual Industries run through the Single-Industry contribution, and then comparing it to the multi-industry contribution results. Is that correct? If so, then you are noticing is correct. The results in summing the single industry contribution will be falsely higher than the results from the multi industry contribution. This is due to the single industry method allowing the Industry(s) to purchase from the other 7 industries. You can verify this by looking at the Detail Results and seeing that if the increase lies in the fact that the target Industries are showing larger than totals when you add the Detail Results inter-Industry and Induced purchases. If you want to look at each of the 8 Industries individually, still follow the multi-industry contribution method. You can use separate Activities with their respective sectors. Please let us know if you have any further questions.
Hello, You certainly can do this for the Direct Effect values, which would be the same as looking at the Study Area Data and dividing the factors over their respective Study Area totals. With respect to the Total results, this becomes a little more difficult to define, so we don't recommend doing it for the Total values, but it is valid for the Direct Effect/Study Area values for the target Industries. Best regards, IMPLAN Group Staff
We have conducted an economic contribution analysis using the multi-industry contribution analysis found on your forum (http://support.implan.com/index.php?option=com_content&view=article&id=366), but instead of lumping all industries in question (production agriculture, industries 1-19 plus other industries such as meat processors, food manufacturers, etc.) into a single scenario (activity with multiple events) we run a scenario for each industry present in the study area and then summarize scenario results. This is in keeping with earlier posts to this forum thread. We've noticed that whereas the sum of individual counties to the state are very close on direct values, the sum of the counties to a state total for indirect and induced are very different. Depending on measure of economic activity, this difference can be 25%-33% lower than what the state numbers are. Comparisons of the sum of congressional district totals to the state are closer, but still quite different than the state (7%-10% lower). Perhaps by running the scenarios separately for each industry (and already having adjusted commodity production and tradeflows for all the rest of the industries in question) the impacts for a given industry for which the scenario is being run understates the impacts from the ones that are not? Could you please help us understand why this is happening? It is very important to our clients (and by extension yours) to be able to have industry-specific results and not just for the aggregated one (e.g., results for each of the 19 agricultural industries and not just a total for all 19 combined). Thanks for your help!
Hello Spencer, Thank you for your forum post. Your individual county contributions will not combine to the same contribution total you find at the state level due to the absence of inter-county trade. Inputs required for production that are not sourced locally are imports. Imports from neighboring counties are leaked from the system, along with any purchases the neighboring county makes from the original county stemming from the impacts of those imports. This inter-county trade is inherently included in a state-level model. You can approximate a distribution of the state impacts to the counties according to each county’s impacts as a proportion of all counties’ impacts (Equation below). CI = County Impact ITC = Impact Total of all Counties ST = State Total (CI[sup]A[/sup]/ITC) * ST = Portion of County A's Contribution to the State Total In regards to your congressional districts, congressional district models are built using the Econometric RPC method, which differs from the Trade model that is used by default for counties and states. Comparing models built using different methodologies will also result in variance. Regards, IMPLAN Staff
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