Estimation of sales decrease caused by a disaster: Hokkaido blackout after earthquake in 2018
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We simulate the inter-firm trading network which consists of approximately 1 million nodes, and we estimate the firm sales in Japan. We apply the gravity interaction model to the real Japanese inter-firm trading network to calculate the money transport between firms. Sales of each firm are evaluated through the scaling relation between the money flow and the sales, and then the total sales are calculated as an economic indicator. This calculation method is applicable to other situations. As an example, we present an estimation of sales decrease caused by the blackout due to the Hokkaido earthquake in September 6, 2018. The total sales are calculated in both cases: before and just after the earthquake. The total loss of sales is estimated as 35 billion yen per day for direct decrease in the firm sales in Hokkaido, while as 90 billion yen per day for indirect decrease in the other areas. The indirect sales decrease is about 2.6 times as well as the direct sales decrease.
KeywordsInter-firm trading network Sales estimation
The inter-firm trading network, or business transaction network, has been one of the key concepts for the understanding of the firm activities. In the context of the complex network systems, the networking between firms with respect to transactions has associated with various properties such as the preferential attachment , the exponential growth of the firms , the scaling relation between degree and sales , and the transport phenomena including network topology [4, 5].
As the theoretical development of the inter-firm trading network, it becomes more and more important practically to forecast the firm activities in the whole country. The direct estimation of the economic indicators needs not only the network structure but also the empirical relations between the structure and the sales. For example, the degree distribution is not the economic indicators itself. The scaling relation helps to calculate the sales distributions, but there is no reason why the scaling relation is still valid in the specific situations or crisis. In other words, we have to remove possibilities of overfitting to the ordinary conditions.
In this study, we present an application of a simulator of the Japanese inter-firm trading network. The simulator calculates the sales of each firm using the network structure and several parameters, based on the gravity interaction model in the inter-firm trading [4, 5]. The physical meanings of parameters are clear in this model. Therefore, we can suppose that some of the parameters are conserved and still valid in other situations.
We compute the sales decrease caused by the blackout in Hokkaido, the northernmost prefecture in Japan, after the earthquake on Sep. 6, 2018 through the gravity interaction model. The sales decrease is categorized into two parts: the direct effect coming from the sales decrease of the firms in Hokkaido area, and the indirect effect coming from those in the other areas. The indirect decrease is about 2.6 times as much as the direct decrease, which implies that the network effect is more important.
We model the Japanese inter-firm trading network as a directed graph, in which the nodes represent the firms and the links represent the transactions. The link directions are set as the same as the money flow: the buyers to the suppliers. The inter-firm transaction data are provided by TDB (Teikoku Databank, Ltd.).
The regional sales decrease caused by the blackout in Hokkaido
Decrease in sales (billion yen) per day
Other than Hokkaido
This research was partially supported by MEXT as “Exploratory Challenges on Post-K computer (Study on multilayered multiscale spacetime simulations for social and economical phenomena)”. This research used computational resources of the K computer provided by the RIKEN Advanced Institute for Computational Science through the HPCI System Research project (Project ID: hp160261, hp170252, and hp180205). This study was partially supported by Teikoku Databank, Ltd., Center for TDB Advanced Data Analysis and Modeling for providing the datasets and the financial support. This study was also partially supported by the Grant-in-Aid for Scientific Research (B), Grant Number 26310207 and JST Strategic International Collaborative Research Program (SICORP) on the topic of “ICT for a Resilient Society” by Japan and Israel.
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