Analysis of the Utilization of Vacant Houses and Extraction of Regional Characteristics Using Travel Information Data

Abstract

The number of vacant houses in Japan has increased rapidly in recent years due to a declining population. The government has been actively developing measures to solve the vacant house problem and has implemented subsidy programs to support the expansion of vacant house utilization projects. Japan has a particularly high number of vacant houses that are utilized for the purpose of “tourism”. However, vacant house utilization projects are scattered across Japan, and information on such projects is lacking. Moreover, the correlation between different vacant house utilization projects and their location characteristics has not been investigated. In this study, we used a travel information website to extract vacant house utilization facilities from the locations listed and determined the location characteristics of the utilization facilities. We classified the extracted utilization facilities into different categories and used the k-means method to group vacant house utilization facilities according to their categories and regional characteristics. The results obtained in this study can help local governments and businesses implement appropriate location-specific utilization projects.

1. Introduction

1.1. Social Background

The population of Japan has been decreasing significantly in recent years; in particular, the population has declined in approximately 82.4% of all municipalities nationwide [1]. Consequently, the number of vacant houses in Japan is increasing. The current number of vacant houses in Japan is the highest ever at approximately 8.49 million, which corresponds to 13.6% of the total number of houses [2]. In particular, the number of vacant houses is expected to increase rapidly owing to the lack of motivation on the part of owners in managing the houses. Poorly managed vacant houses lead to various problems, such as aesthetic degradation, inadequate hygiene, collapse of houses, trespassing, illegal occupation, arson, and other threats to public safety.

The Act on Special Measures for Promoting Vacant House Countermeasures was enacted in May 2015 to address the aforementioned issues, and a vacant house countermeasure framework was established at the level of local government [3]. The Vacant House Countermeasures Comprehensive Support Project was launched in 2016 to support the implementation of vacant house countermeasure plans. These measures have helped address vacant house issues by supporting local governments working on comprehensive vacant house countermeasures. Vacant house countermeasures include the removal, utilization, and sale of houses. Utilization of houses is particularly advantageous because it is cheaper than constructing new houses and is subsidized by local governments. The utilization of vacant houses has been proactively promoted in Japan in recent years. For instance, local governments have set up “vacant house banks” that standardize information on vacant houses, while nonprofit organizations such as Vacant House Utilization Support have increased their activities.

Old folk houses and old homes exemplify the architectural techniques and living customs of Japan and, hence, have a very high cultural value. These characteristics evoke a sense of freshness and nostalgia among people residing in urban areas and foreigners unfamiliar with Japanese architecture. Consequently, old folk houses have attracted attention as a tourist resource. In Soka-juku (Saitama Prefecture) and Unuma-juku (Gifu Prefecture), old folk houses in post-station towns are leading tourist destinations [4]. Tourism town development using vacant house utilization facilities is also being pursued in various places with the aim of regional revitalization. In Ojika Town, which is an isolated island in Nagasaki Prefecture, old folk houses, such as samurai residences and old family mansions, are being utilized as accommodation facilities wherein entire buildings are rented out [5]. These projects, called old folk house stays, were initiated by island residents with the objective of protecting vacant old folk houses on the island and preserving the scenery and culture of the island for future generations.

The Tourism Town Development Utilizing Historical Resources [6] project by the Cabinet Secretariat has focused on companies and historical resources for developing vacant houses as tourism resources. Although an outline of the initiative and organizational form has been established, an understanding of the impact of the project on the surrounding region and its relationship with location characteristics is lacking. In addition, vacant houses are used by private companies for housing distribution. Moreover, numerous companies and corporations utilize vacant houses. However, the locations and characteristics of these houses are unclear. Business operators or consultants working on vacant house utilization projects usually examine previous cases to understand trends. As the number of vacant houses is expected to increase rapidly in the future, organizing information on vacant houses and understanding the ground realities of such projects are critical.

1.2. Purpose of This Study

In Japan, projects that utilize vacant houses are being promoted in line with the increasing number of vacant houses. Meanwhile, stakeholders have not understood the current situation and characteristics of vacant house utilization businesses as a tourism resource that can attract visitors, and the actual circumstances of regional characteristics and uses need to be clarified. In this study, we extracted examples of vacant house utilization in tourist locations and determined their characteristics using a travel information website that allows users to search and compare tourist locations, accommodation facilities, tours, and other travel information in Japan and overseas as well as to read reviews. We classified each example based on the utilization category and location characteristics. The classification of vacant house utilization projects can clarify the correlation between location characteristics and utilization category. Such a classification is expected to help businesses select categories and locations for vacant house utilization projects. Numerous vacant house utilization projects in Japan have been forced to withdraw or have been canceled after the start of the project due to a lack of profitability. Hence, the correlation between the utilization category and location characteristics derived in this study can help businesses choose appropriate and location-specific utilization projects, which can, in turn, promote sustainable vacant house utilization.

Figure 1 shows an outline of the study. We first searched for keywords related to vacant house utilization among the tourist locations listed on the travel information website “Jalan.net” and extracted information from the search results. Jalan.net is a widely used tourist information site, and the utilization facilities listed on Jalan.net are likely to have a reasonable number of users. The extracted facilities were divided into different categories (Step 1). The addresses of the utilization facilities were plotted in ArcGIS, and basic data on the regional characteristics of the municipalities in which the facilities are located were used to clarify the characteristics of each category (Step 2). Cross-tabulation was used to visualize the regional characteristics by category. The k-means method was used to group vacant house utilization facilities and clarify their characteristics (Step 3). The k-means method enabled the classification of utilization facilities, and the characteristics of each group were captured using graphs.

2. Summary of Previous Studies and Positioning of This Study

This study presents a basic analysis of the characteristics of vacant house utilization projects using data from a travel information website and proposes a classification of the utilization projects. There have been several studies with similar objectives wherein vacant house utilization projects in tourist destinations have been investigated using data from travel information websites. In this section, previous studies are summarized according to the following two points in order to position the present study.

• General analysis of the current status of vacant house utilization
• Research focusing on utilization projects for tourism purposes

2.1. Summary of Previous Studies

First, we summarize the general research on the current status of vacant house utilization. Kim et al. [7] collected vacant house utilization data via interview surveys at selected prefectures, categorized and visualized the management systems of 14 projects, and clarified the relationship between the project implementation entity and the affiliated organizations through case studies. Tamai et al. [8] examined the current status and future potential of the process from crowdfunding (CF)-based property contracts and vacant house renovation to utilization. Vacant house utilization cases were extracted from the recruitment sites of CF management companies, and the actual circumstances of the business and characteristics of CF were discussed through tabulation. Nakada et al. [9] obtained data on 203 old folk houses from local governments and chambers of commerce in one city and nine prefectures, mainly in the Kanto region, and clarified the current status and trends of old folk house use through a basic compilation. They also discussed these issues and their potential. Koreman et al. [10] analyzed two Dutch cases of the commercial reuse of vacant farm buildings in relation to rural development. They suggest that the commercial reuse of vacant farm buildings can attract new entrepreneurs, employment, and vitality to rural areas. Kim et al. [11] demonstrated that the success of integrated urban green infrastructure systems on vacant lots can help planners, developers, designers, and occupants better understand their potential value and make better use of these spaces. Heesun et al. [12] proposed an effective vacant house management plan by exploring the characteristics of vacant houses at the local level in Korea by zoning, such as residential and commercial, and analyzing the factors that affect them.

Next, we summarize studies that focus on the utilization of vacant houses for tourism purposes. Mizoguchi et al. [13] clarified the trends of old folk house utilization in the historical city area of Omihachiman City, Shiga Prefecture, and explored the factors that promote such utilization. They conducted interviews with the relevant businesses in the target area and clarified the factors leading to the establishment of property contracts and renovations, as well as the history and conditions of the establishment. Takehana et al. [14] investigated the utilization of vacant houses in historical streetscapes and their factors. They examined the potential of utilizing vacant houses in the target area. They concluded that the establishment of a town development system that facilitates the renovation of vacant houses, as well as the implementation of utilization measures that consider regional characteristics, are necessary for utilizing vacant houses in historical townscapes. Arbara et al. [15] focused on the potential evolution of Airbnb housing compared to the traditional rental and housing market through the case of Venice. The findings of a theoretical population game model are tested and discussed using a dataset describing its use over the past 20 years.

2.2. Positioning of This Study

Kim et al. [7], Tamai et al. [8], and Koreman et al. [10] presented a general analysis of the current status of the vacant house utilization projects, clarified the management system, funding, and business activities, and discussed appropriate policies. Nakada et al. [9] categorized vacant house projects based on their utilization purpose and investigated the status of the projects via interviews with businesses. Mizoguchi et al. [13], Takehana et al. [14], and Arbara et al. [15] focused on tourist destinations and historical preservation districts to understand the current status and future potential of vacant house utilization projects. However, to the best of our knowledge, the correlation between vacant house utilization projects across the nation and their location has not been investigated. In this study, we used a tourist information site to tabulate and classify vacant house utilization projects; hence, the data used herein differ from those of previous studies. Moreover, we investigated the correlation between the current status of vacant house utilization projects across the nation and their location characteristics.

3. Data Extraction and Classification of the Facilities

3.1. Extraction of Utilization Facilities Using Travel Information Website

In this study, we used the travel information website Jalan.net [16] to identify tourist facilities that utilize vacant houses across the nation. Jalan.net is a widely used travel and tourism information site and has the highest number of annual users of any travel site in Japan [17] (Figure 2). In this study, we used Jalan.net, a well-known website in Japan, to examine more data on the utilized facilities. The website has been used to obtain analytical data on the status of tourist facilities; for example, Okawa et al. [18] used data from Jalan.net to clarify the perceptions of tourist destinations using word-of-mouth reviews via text mining and language analysis.

First, we extracted vacant house utilization cases by searching for the following five keywords among the tourist locations, gourmet locations, and accommodation locations listed on Jalan.net: “vacant house”, “utilization”, “reuse”, “old folk house”, and “renovation.” We then scraped the results using Beautiful Soup, which is a library for parsing HTML pages. From the extracted information, 1314 cases were used as data for this analysis; facilities that did not fit the objective of this study were excluded. Here, “utilization facilities” are defined as “houses and facilities that were once used or have been abandoned as vacant houses but are now being used for a different purpose”.

Table 1. Summary of data obtained from “Jalan.net”.

	Items	Description
Information about the locations	Name	Name of the location
	Summary	Description of the location
	Address & Postal code	Detailed address
	Category of use	✓ Gourmet locations ✓ Accommodation locations ✓ Tourist locations
	Number of reviews	Number of reviews posted for each location

details the data corresponding to each location. Basic information such as location name, address, and location explanation can be obtained. In addition, the categories to which the location belongs, such as “gourmet, accommodation, and tourist,” can also be calculated.

3.2. Classification and Location of Utilization Facilities

The extracted facilities were roughly classified into three categories: tourist locations, gourmet locations, and accommodation locations. These categories were used in the present study. Figure 3 shows the distribution of facilities according to category. The number of “gourmet locations” was the highest, with 720 cases, followed by “accommodation locations” with 465 cases, and “tourist locations” with 129 cases. Figure 4 shows the geographical distribution of the facilities.

4. Actual Situation of Utilization Vacant Houses in Japan

In this section, we focus on the regional characteristics of the locations of the facilities obtained via data extraction and aim to understand the characteristics of the facilities via basic tabulations.

First, we extracted information on the municipal locations of each facility using address data. We then obtained information on the total population, aging rate, population density, and suitability of depopulated areas for the respective municipalities using data from the 2020 Population Census [19] and National Prefectural and Municipal Area Survey [20]. The average values of these data for each case were then calculated.

Figure 5 shows the data for the total population. Accommodation locations tended to be located in municipalities with the lowest population, whereas gourmet locations tended to be located in municipalities with the highest population. Thus, regions far from urban areas and with low populations have a higher number of accommodation locations, whereas regions with large populations, where customers are expected, have a higher number of gourmet locations. However, the standard deviation was large, and the difference in the number of vacant house locations by use in the total population was small.

Figure 6 shows the data corresponding to the population density. Accommodation locations tended to be located in municipalities with the lowest population density, whereas gourmet and tourist locations tended to be located in municipalities with a higher population density. Accommodation facilities are considered to be located in suburban and rural regions with a low population density wherein people can spend a quiet night in an old folk house, whereas gourmet and tourist locations are considered to be located in densely populated urban areas to attract customers and tourists during the daytime. The standard deviation for population density was large, and the difference in population density between vacant house utilization categories was thought to be minimal.

Figure 7 shows the data for the aging rate. Gourmet and tourist locations tended to be located in municipalities with a low aging rate, whereas accommodation locations tended to be located in municipalities with the highest aging rates. Gourmet locations were considered to be predominantly located in regions with a low aging rate and many young people, and accommodation locations were more common in quieter regions far from cities with a high aging rate.

Figure 8 shows the proportion of locations located in the depopulated regions. Accommodation locations tended to be located in the most depopulated regions, whereas gourmet locations tended to be located in the least depopulated regions. Depopulated regions are not considered vibrant areas in the local community, and accommodation locations can help revitalize those regions. In contrast, non-depopulated regions are considered vibrant areas of the municipality, and gourmet locations can help further improve their tourism appeal.

5. Classification of Utilization Projects Using the k-Means Method

The characteristics of the regions in which vacant house utilization facilities are located are clarified in Section 4. In this section, we grouped the vacant house utilization facilities by their uses and regional characteristics to clarify their characteristics.

5.1. Overview of the Analysis

Data corresponding to the three categories (detailed in Section 3) and the regional characteristics of the facilities (detailed in Section 4) were used. The k-means method was used to classify vacant house facilities and clarify their characteristics.

The k-means method is an analysis that measures the distance between multiple variables and similar groups using a small number of variables, enabling the interpretation of the characteristics of the group from the analysis results.

Table 2. Summary of the explanatory variables used in the k-means method.

Item 1.	Item 2.	Data Type	Example of Data
Data on use	Tourist locations	Qualitative	1: applicable 0: not applicable
	Gourmet locations	Qualitative	1: applicable 0: not applicable
	Accommodation locations	Qualitative	1: applicable 0: not applicable
Data on regional characteristics	Population	Quantitative	(Ex) 103.6 K
	Aging rate	Quantitative	(Ex) 25.47 %
	Population density	Quantitative	(Ex) 276.32 per square kilometer
	Depopulated regions	Quantitative	1: applicable 0: not applicable

shows the explanatory variables used in this analysis. The three categories detailed in the previous section were used as dummy variables for each facility: the dummy variable was set to “1” if the facility belonged to the respective category and was set to “0” if the facility did not belong to the respective category. The population, aging rate, population density, and suitability of the depopulated regions for the municipalities where each facility was located were also extracted and are shown in Table 2. The population, aging rate, population density, and suitability of depopulated regions, which indicate regional characteristics, are representative figures that indicate Japan’s land infrastructure.

5.2. Results of Analysis and Actual Situation of Utilization Cases

The clusters were classified using the k-means method. The number of clusters was determined using the elbow method, which determines the optimal number of clusters based on the mean sum of the errors within the clusters. The elbow method estimates the appropriate number of clusters by plotting a value that minimizes the following equation while changing the number of clusters:

$${\sum }_{i=1}^k{\sum }_{p\in C_i}{\left(p-c_i\right)}^2,$$

where $k$ is the number of clusters, $C_i$ is the set of data points in the $i$th cluster, and $c_i$ is the center of gravity of $C_i$. The point corresponding to the maximum change in the slope of the line in the elbow method was determined to be the appropriate number of clusters. The results obtained are shown in Figure 9. Based on these results, the number of clusters was set to four, and a k-means analysis was conducted. Figure 10 and Figure 11 show the results of the k-means analysis.

Table 3. Interpretation of the results of the k-means method.

	Data on Use			Data on Regional Characteristics
Cluster	Tourist Locations	Gourmet Locations	Accommodation Locations	Population	Aging Rate	Population Density	Depopulated Regions
Cluster 1	◎	〇	〇	〇	〇	△	×
Cluster 2	◎	△	◎	×	◎	×	〇
Cluster 3	◎	〇	〇	△	〇	〇	×
Cluster 4	△	◎	×	◎	△	◎	×

shows the interpretation of each cluster using the k-means method.

Cluster 1 is a group with low population density that is not depopulated: it could be interpreted that the utilization of tourist locations tends to be high. Cluster 2 is a group with a low population, high aging rate, low population density, and a high proportion of depopulated regions: it could be interpreted that the utilization of tourist and accommodation locations tends to be high, and the utilization of gourmet locations tends to be low. Cluster 3 includes regions with low populations and a low proportion of depopulated regions; it could be interpreted that the utilization of tourist locations tends to be high. Cluster 4 is a group with a high population, low aging rate, high population density, and is not depopulated: it could be interpreted that the utilization of gourmet locations tends to be high, and the utilization of accommodation and tourist locations tends to be low.

Thus, grouping the utilization, uses, and regional characteristics via the k-means method enabled the clarification of the characteristics of each category.

In this study, we clarified the relationship between the use of vacant houses and regional characteristics. This will enable operators utilizing vacant houses to smoothly select the use of vacant houses in accordance with regional characteristics. Furthermore, we believe that this will promote the sustainable use of vacant houses and solve the problem of vacant houses in Japan.

6. Summary and Future Works

In this study, we focused on projects that utilize vacant houses as part of countermeasures against vacant houses and clarified the basic characteristics of vacant house utilization projects nationwide. Information on the utilization of vacant houses for tourism was obtained by scraping a travel information website. The information obtained was classified into three utilization categories. The regional characteristics of the facilities were clarified based on population, aging rate, population density, and suitability of the depopulated region for the municipal location of the facility.

The regional characteristics of each location were grouped based on the k-means method for utilization and use, which enabled the clarification of characteristics for each use.

A limitation of this study is that the vacant house utilization examined herein was focused on tourism alone, and the data were obtained using a travel information website. In future work, other search methods and questionnaire surveys could be used to compile other cases of vacant house utilization, such as welfare and salon facilities. We also intend to focus on the demand for and maintenance of vacant houses used in the tourism industry, obtain specific data on the issues and continuity that have arisen in each case, and understand the current circumstances. Moreover, some of the cases searched for and extracted in this study did not correspond to vacant house utilization facilities. Therefore, the search methodology may need to be improved. Furthermore, this study focused on regional characteristics to understand the actual circumstances. We intend to examine the geographical characteristics of the facilities, as well as the issues experienced by neighboring residents. We think geographical characteristics are closely related to user movements. In Japan, there are many regions with high tourism incomes and aging populations. We believe that when selecting the use of vacant houses in these areas, it is necessary to consider users from outside and the aging population in adjacent areas. Therefore, we will first identify the proximity to the main urban centers/agglomerations and the characteristics of adjacent areas. Furthermore, we believe that it is necessary to clarify the relationship between these characteristics and the use of utilized vacant houses.