Ⅲ
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)
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
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.
”Network Analysis of the Gender Gap in International Remittances by Migrants”
Zelda Marquardt, Yuichi Ikeda
Rev Socionetwork Strat 16, 337–376 (2022)
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.
”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, 2022/08
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.
”Network analysis of attitudes towards immigrants in Asia”
Rachael Kei Kawasaki, Yuichi Ikeda
Applied Network Science ,5 , 1, 2020/12
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, 2010/08
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.
”International comparison of labor productivity distribution for manufacturing and non-manufacturing firms”
Y. Ikeda, W. Souma
Progress of Theoretical Physics Supplement, 179, 93-102, 2009
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.