Human Flow 人の流れ


Human Flow



“Community Structure and Its Stability on a Face-to-Face Interaction Network in Kyoto City ”

Yu Ohki, Hitomi Tanaka, Yuichi Ikeda

Journal of the Physical Society of Japan 
92, 034804 (2023)

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 As social behavior plays an essential role in people’s lives, the features of face-to-face interaction networks must be examined to understand people’s social behavior. In this study, we focused on the stable community structure of a face-to-face interaction network because it explains the persistent communities caused by the stationary communication patterns of citizens and visitors in a city. We regarded citizens and visitors as two kinds of particles and the community as a phase and theorized the stability of the community structure using the equilibrium conditions among communities. We formulated the chemical potentials of the communities and examined whether they were in equilibrium under the assumption of a canonical ensemble. We estimated the chemical potentials of persistent communities and found that these values matched within approximately 10% error for each day. This result indicates that the cause of persistent communities is the stability of community structure.




“Optimizing travel routes using temporal networks constructed from globalpositioning system data in kyoto tourism ”

Tatsuro Mukai , Yuichi Ikeda

Front. Phys., 24 November 2022
Sec. Interdisciplinary Physics
Volume 10 - 2022

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 Owing to the complexity of urban transportation networks and temporal changes in traffic conditions, the assessment of real-time traffic situations is a challenge. However, the development of mobile information devices using the global positioning system (GPS) has made it easier to obtain personal mobility information. In this study, we developed a method for evaluating the mobility of people in a city using GPS data. We applied two methods: evaluating human mobility using temporal networks constructed from GPS data, and searching for the shortest path by constructing and solving the time-dependent traveling salesman problem (TDTSP). The estimation is expected to be more realistic if transportation delays from congestion are considered. This study makes two major contributions. First, we propose a new method for estimating the time weights of edges in temporal networks using probability density functions for the travel time. Second, to apply ant colony optimization to the TDTSP, we propose a new method for estimating the congestion level from GPS data and calculating the transition probability using the estimated congestion level. As a case study, we conducted a human mobility analysis in Kyoto City. 

  都市交通網は複雑であり、交通状況も刻々と変化するため、リアルタイムの交通状況の把握は困難である。しかし、GPS(Global Positioning System)を用いた携帯情報端末の発達により、個人の移動情報を容易に取得することができるようになった。そこで本研究では,GPSのデータを用いて,都市における人の移動度を評価する手法を開発した.GPSデータから構築した時間ネットワークを用いて人の移動度を評価する方法と,時間依存巡回セールスマン問題(TDTSP)を構築し解くことで最短経路を探索する方法の2つを適用した.渋滞による交通機関の遅延を考慮した場合、より現実的な推定が可能になると考えられる。本研究は2つの大きな貢献をしている。第一に、移動時間に対する確率密度関数を用いて、時間ネットワークにおけるエッジの時間重みを推定する新しい方法を提案することである。第二に、TDTSPにアントコロニー最適化を適用するために、GPSデータから混雑度を推定し、推定された混雑度を用いて遷移確率を計算する新しい方法を提案する。事例として、京都市における人の移動の分析を行った。 



“Network Analysis of the Gender Gap in International Remittances by Migrants ”

Zelda Marquardt, Yuichi Ikeda

Rev Socionetwork Strat 16, 337–376 (2022)

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Financial inclusion is considered a key enabler of international development goals. Despite the expansion of financial access overall, the gender inequalities in basic access have remained consistent. This research investigates the predictive power of global remittance and migration flows on the gender gap in financial inclusion. First, singular value decomposition is applied to the World Bank’s 2017 Global Findex data to identify the financial inclusion variables that most contribute to the gender gap in financial inclusion. We find that indicators pertaining to account ownership, emergency funding, and receiving payments are especially significant. Based on the identified variables, a novel Financial Inclusion Gender Gap Score is calculated for 143 economies. The score is then incorporated into a complex network analysis of global remittance and migration networks. We analyze how network features such as node attributes, community membership, and bow-tie structure can be used to make inferences about the magnitude of a financial inclusion gender gap. Our findings suggest that weaker linkages in the network, characterized by lower node strength and peripheral positions in the bow-tie structure, are determinants of a notable financial inclusion gender gap. We also highlight communities in the remittance and migration networks with a more substantial gender imbalance, and discuss the the social- and cultural-leaning factors driving community formation in the migration network that seem to predicate a greater gap.  

 金融包摂は、国際的な開発目標を実現するための重要な要素であると考えられています。金融アクセスが全体的に拡大しているにもかかわらず、基本的なアクセスにおける男女の不平等は一貫している。本研究では、金融包摂におけるジェンダー格差に対する世界の送金・移住の流れの予測力を調査している。まず、世界銀行の2017年版Global Findexデータに特異値分解を適用し、金融包摂のジェンダー格差に最も寄与する金融包摂変数を特定する。その結果、口座の所有、緊急時の資金調達、支払の受領に関わる指標が特に重要であることが分かった。特定された変数に基づいて、143のエコノミーについて新規の金融包摂ジェンダー・ギャップ・スコアが算出されます。このスコアは、世界の送金・移住ネットワークの複雑なネットワーク分析に組み込まれます。我々は、ノードの属性、コミュニティーのメンバーシップ、ボウタイ構造などのネットワークの特徴が、金融包摂のジェンダーギャップの大きさについての推論を行うためにどのように使用できるかを分析する。その結果、ノードの強度が低く、ボウタイ構造における周辺的な位置によって特徴づけられるネットワーク内の弱いつながりが、顕著な金融包摂ジェンダーギャップの決定要因であることが示唆された。また、送金ネットワークと移住ネットワークにおいて、より実質的なジェンダーの不均衡があるコミュニティを強調し、より大きなギャップを前提としていると思われる移住ネットワークにおけるコミュニティ形成を推進する社会的・文化的な要因について議論した。 


“Regional medical inter-institutional cooperation in medical provider network constructed using patient claims data from Japan ”

 Yu Ohki ,Yuichi Ikeda ,Susumu Kunisawa,Yuichi Imanaka 
 PLoS ONE 17(8): e0266211,

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The aging world population requires a sustainable and high-quality healthcare system. To examine the efficiency of medical cooperation, medical provider and physician networks were constructed using patient claims data. Previous studies have shown that these networks contain information on medical cooperation. However, the usage patterns of multiple medical providers in a series of medical services have not been considered. In addition, these studies used only general network features to represent medical cooperation, but their expressive ability was low. To overcome these limitations, we analyzed the medical provider network to examine its overall contribution to the quality of healthcare provided by cooperation between medical providers in a series of medical services. This study focused on: i) the method of feature extraction from the network, ii) incorporation of the usage pattern of medical providers, and iii) expressive ability of the statistical model. Femoral neck fractures were selected as the target disease. To build the medical provider networks, we analyzed the patient claims data from a single prefecture in Japan between January 1, 2014 and December 31, 2019. We considered four types of models. Models 1 and 2 use node strength and linear regression, with Model 2 also incorporating patient age as an input. Models 3 and 4 use feature representation by node2vec with linear regression and regression tree ensemble, a machine learning method. The results showed that medical providers with higher levels of cooperation reduce the duration of hospital stay. The overall contribution of the medical cooperation to the duration of hospital stay extracted from the medical provider network using node2vec is approximately 20%, which is approximately 20 times higher than the model using strength.  

 世界人口の高齢化に伴い、持続可能で質の高い医療制度が求められている。医療協力の効率性を調べるために、患者の請求データを用いて医療提供者と医師のネットワークを構築した。これまでの研究により、これらのネットワークには医療連携に関する情報が含まれていることが示されている。しかし、一連の医療サービスにおける複数の医療提供者の利用形態については考慮されていない。また,これらの研究では医療連携を表現するために一般的なネットワーク特徴量のみを用いており,その表現力は低いものであった.これらの限界を克服するため、本研究では、医療者ネットワークを分析し、一連の医療サービスにおける医療者間の連携が提供する医療の質に対する全体的な貢献度を検討した。本研究では、i) ネットワークからの特徴抽出方法、ii) 医療従事者の利用形態の取り込み、iii) 統計モデルの表現力に着目した。対象疾患として大腿骨頚部骨折を選択した。医療機関ネットワークを構築するために、2014年1月1日から2019年12月31日までの日本の一都道府県の患者請求データを分析した。モデルは4種類を検討した。モデル1と2はノード強度と線形回帰を使用し、モデル2は患者の年齢も入力として取り入れた。モデル3と4は、線形回帰と機械学習手法である回帰木アンサンブルを用いたnode2vecによる特徴表現を用いている。その結果、医療連携度が高い医療者ほど入院期間が短くなることがわかった。node2vec を用いて医療機関ネットワークから抽出した在院日数に対する医療連携の全体寄与度は約 20%であり,強度を用いたモデルの約 20 倍であった. 


“Network analysis of attitudes towards immigrants in Asia ”

Rachael Kei Kawasaki, Yuichi Ikeda, 
Applied Network Science ,5 , 1, 

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 This study models cross-national attitudes towards immigrants in East and Southeast Asia as a signed and weighted bipartite network of countries and evaluative reactions to a variety of political issues, or determinants. This network is then projected into two one-mode networks, one of countries and one of determinants, and community detection methods are applied. The paper aims to fill two deficiencies in the current research on attitudes towards immigrants: 1) the lack of cross-national studies in Asia, a region where migration is growing, and 2) the tendency of researchers to treat determinants as uncorrelated, despite the interdependent nature of evaluative reactions. The results show that the nine countries in the sample are a cohesive clique, showing greater similarities than differences in the determinants of their attitudes. A blockmodeling approach was employed to identify eight determinants in attitudes towards immigrants, namely views on independence and social dependencies, group identities, absolute or relative moral orientation, attitudes towards democracy, science and technology, prejudice and stigma, and two determinants related to religion. However, the findings of this survey yielded some surprising results when compared with the literature review. First, education was not found to be a significant determinants of attitudes towards immigrants, despite its strong and consistent predictive power in European models. Second, prejudice appears to be mediated in part by religion, especially in religious identification and belief in God. Group identity and prejudice also appear to be related, though only weakly. Finally, anxiety appears in clusters related to social norms, suggesting that fears regarding immigrants relates closely to expectations of others’ behavior. 


“Analysis of labor productivity using large-scale data of firm’s financial statements”

Y. Ikeda, W. Souma, H. Aoyama, Y. Fujiwara, H. Iyetomi, 

European Physical Journal B, 76, 4, 491-499,

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We investigated labor productivity distribution by analyzing large-scale financial statement data consisting of listed and unlisted Japanese firms to clarify the characteristics of the Japanese labor market. Both high and low productivity sides of the labor productivity distribution follows the power-law distribution. Large inequality in the low productivity side was observed only for the manufacturing sectors in Japan fiscal year (JFY) 1999 and observed for both the manufacturing and non-manufacturing sectors in JFY 2002. The decline in the Japanese GDP in JFY 1999 and JFY 2002 were coincided with the large inequality in the low productivity side of the distribution. A lower peak was found for all non-manufacturing sectors. This might be the origin of the low productivity of the non-manufacturing sectors reported in recent economic studies.

本研究では、日本の労働市場の特徴を明らかにするために、日本の上場企業と非上場企業の大規模な財務諸表データを分析し、労働生産性の分布を調べた。その結果、労働生産性分布の高生産性側、低生産性側ともに力法則分布に従っていることが明らかになった。低生産性側の格差が大きいのは,1999 年度の製造業のみであり,2002 年度には製造業と非製造業の両方で観測されている。1999 年度と 2002 年度の日本の GDP の低下は、分布の低生産性側の格差の大きさと重なっている。非製造業のすべての部門で低いピークが見られた。これが最近の経済研究で報告されている非製造業の生産性の低さの原因ではないかと考えられる。

“International comparison of labor productivity distribution for manufacturing and non-manufacturing firms”

Y. Ikeda, W. Souma,
Progress of Theoretical Physics Supplement, 179, 93-102,

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Labor productivity was studied at the microscopic level in terms of distributions based on individual firm financial data from Japan and the US. A power-law distribution in terms of firms and sector productivity was found in both countries' data. The labor productivities were not equal for nation and sectors, in contrast to the prevailing view in the field of economics. It was found that the low productivity of the Japanese non-manufacturing sector reported in macro-economic studies was due to the low productivity of small fims.



Commodity Flow



Monetary Flow



Human Flow



Decarbonized energy system



Economic Collective Motions