Recherche FFJ Research Statement Akiko SAKANISHI


Changes in family formation and urban structure: A comparison between French and Japanese metropolitan areas


Ritsumeikan University



The increase in living alone and re-urbanization have been observed in both France and Japan. This study analyzes changes in socio-demographic conditions in the central city and the suburbs of large metropolitan areas in France and Japan. No study has ever explored the comparative analysis of family formation and urban structure in France and Japan. The findings obtained by this research should be of special interest to urban and demographic policymakers in each country.

Background and aim

The sharp rise of single-person households and the re-urbanization tendency have become prominent in several of the largest Japanese metropolitan areas in the 2000s. The increasing trend of living alone and re-urbanization has been observed in large French metropolitan areas since the 1980s.

This study analyzes changes in population and the number of single-person households by sociodemographic characteristics, including age and sex, in the central city and suburbs, respectively, for large French and Japanese metropolitan areas.

We examine the stages of urbanization in the large metropolitan areas in each country and consider their relation to changes in the family formation. The results would include similarities and differences in both countries, where we could learn from the specific characteristics of the other country.

Changes in family formation and urbanization processes in Japan

Japan’s population has been ageing at a remarkable rate since the 2000s. In Japan, according to the 2000 population census, the ageing rate, defined as the share of the population aged 65 and over, was 17.4% in 2000. The value increased dramatically, reaching a record-breaking 29.1% in 2022.

Low fertility resulting from an increase in non-marriage and late marriages has been the primary cause of Japan's rapid population ageing over the past several decades. These changes in marriage behaviour have resulted in a reduction in family size. Living alone has been a rapidly growing trend in recent decades. For the prime working-age population aged 25–59, the proportion of single-person households in 2000 was 10.3% and 33.7% for the total and unmarried people, respectively. Increased numbers of people marrying later in life or remaining unmarried have contributed to the rise in the number of individuals living alone. This trend is particularly common in big cities.

Sakanishi (2011) showed that young people in their twenties have a strong propensity to move alone, without their families, and live in single-person households in their new place of residence. Tokyo metropolitan area has seen a positive net in-migration of young people since the 1950s, which has intensified the Japanese population in this area. The percentage of single-person households among the working-age population is increasing rapidly in central cities due to a large increase in the percentage of unmarried people and a large influx of people from rural areas. Kawashima, Fukatsu, and Hiraoka (2007) found a clear trend of re-urbanization in the Tokyo metropolitan area using the ROXY-index, which allows us to measure the stages of the urbanization process. These changes in household structure caused by the sharp increase in unmarried people are considered to be associated with the re-centralization of the population, which has been evident in the Tokyo metropolitan area since the 2000s.

Changes in family formation and its socio-economic impacts in France and other European countries

Previous studies have considered the rising tendency to live alone and its socioeconomic impacts in France and other European countries.

Ogden and Hall (2000) analyzed household structure and population change for the 10 largest cities in France from 1975 to 1990. They showed that single-person households increased in all cities during that period, and for 1982–1990, most cities experienced a population recovery in the central cities as compared to 1975–1982.

According to Wall (1989), since World War II, the share of single-person households to all households has increased in most European countries, and a decline of the average household size, non-marital cohabitation, and a sharp increase in the number of one-parent families have been observed. Esteve et al. (2020) performed a cross-national analysis of living alone by age and sex using data from 113 countries and found significant cross-national differences in living alone even when the data was standardized by marital status. Their findings showed that the proportion of people living alone is dependent on age. Over the age of 50, this proportion increases with age, and it is very steep for women. Quintano and D’Agostino (2006) analyzed income inequality among single-person households in France, the U.K., Germany, and Italy and found that the poverty rate was higher in Italy than in other countries. According to their results, cross-national poverty was slightly explained by the disparities in the distribution of personal characteristics among the countries.

As discussed by Ogden and Hall (2000), the increase in living alone and the population recovery in the central cities emerged in the 1980s in France. Salvati et al. (2019) analyzed population dynamics in 129 European metropolitan regions for two periods: economic expansion (2000–2007) and economic recession (2008–2014). According to the results of their study, the number of cities that indicated re-urbanization trends was 36% in 2000–2007 and 47% in 2008–2014, showing a sharp increase.

Overall, living alone and re-urbanization have been increasingly predominant trends over the past few decades. Previous studies have discussed socioeconomic factors explaining the rise of living alone. Changes in marital behaviour, such as later marriage and nonmarriage, are an important cause of the increase in single-person households. The proportion of living alone is associated with age and sex. Reher and Requena (2018) analyzed living alone of older people aged 65 and over by sex and showed that solitary living was more dominant for women than men. The rate of living alone for elderly people is considerably high, particularly for women, because becoming widowed and living apart from children increase with age for older people. In this sense, as the population ages, the number of single-person households must increase. Other factors affecting living arrangements consist of various socioeconomic characteristics such as changes in lifestyle, increased number of highly educated individuals, in-migration from rural areas, and changes in family structure and marital behaviour.

Method and contribution of this research

This research analyzes population changes in the central cities and suburbs in French and Japanese large metropolitan areas for recent decades using the data of censuses in each country to investigate and compare urbanization processes in each country. The traditional urban development model proposed by Klaassen et al. (1981) classified the urban cycle into four stages based on population changes in the core of the city and the periphery. This study utilizes the data of large Japanese and French metropolitan areas in discrete years and examines the growth patterns of urban development. We evaluate the stage of urban development in each metropolitan area. We compare the differences in the stages of the urban cycle between France and Japan and their changes over time.

Factors contributing to urban agglomeration, and migration from rural to urban areas have been widely researched so far. Compared to it, few studies have clarified the factors of re-urbanization, although it has been a growing tendency both in French and Japanese large cities.

This study investigates the relationship between changes in family formation, specifically the increase in living alone and re-urbanization in French and Japanese large cities, while referring to factors affecting the residential choices of individuals.

A comparative study of metropolitan areas should consider the following differences in socioeconomic characteristics between France and Japan: 1) the role of marriage, 2) the housing market, and 3) the size and core¬¬-periphery structure of the metropolitan area.

It needs to be noticed that there are differences in marriage behaviour and housing market conditions between Japan and France, and their impact on individuals’ mobility differs between the two countries. In Japan, 98% of births were children of married couples in 2018. A significant part of the decline in the fertility rate is explained by the rise in unmarried rates. Most single unmarried people do not have children. On the other hand, only about 40% of births were those of married couples in France in 2018. In France, marriage is not necessarily a requirement for child rearing or married life. The role of marriage differs between Japan and France. The rise in Japan’s unmarried rate is more likely to reflect the changes in the family structure. Thus, the role of singles in re-urbanization would be more emphasized in Japan’s study.

As for the housing market, housing affordability is different in the two countries. Land prices in Japanese large cities have stagnated for more than two decades. The re-urbanization tendency in the Tokyo and Osaka metropolitan areas since the 2000s was induced by stagnant housing prices in the central cities, which made them affordable to various individuals. In contrast, housing prices showed unabated growth in France. This leads to the fact that in the French case, adults with high income who can live alone in metropolitan areas and afford a rental or purchase of an apartment are privileged. The impact of the land price on the re-urbanization tendency is very different between Japan and France. It is necessary to take the differences in the role of marriage and the housing market condition between both countries into consideration in the comparative analysis.

Besides, the structure of metropolitan areas in both countries is different in terms of size and the relationship between the centre and peripheries. Therefore, this research should explore a case study for a comparison of urban areas with similar structures.

The results will help us understand similarities and differences in demographic characteristics and urban structure of both countries and the factors explaining them. The comparison of family formation and urban organization in both countries has never been investigated. We can find lessons and significant policy implications from the specific characteristics of the other country.


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Kawashima, T., Fukatsu, A., & Hiraoka, N. (2007). Re-urbanization of Population in the Tokyo Metropolitan Area: ROXY-index / Spatial-cycle Analysis for the Period 1947–2005, The journal of Faculty of Economics, Gakushuin University, 44 (1), 19 – 46.

Ogden, P. E., & Hall, R. (2000). Households, Reurbanisation and the Rise of Living Alone in the Principal French Cities, 1975-90. Urban Studies, 37 (2), 367–390.

Wall, R. (1989). Leaving Home and Living Alone: An Historical Perspective. Population Studies, 43 (3), 369–389.

Esteve, A., Reher, D. S., Trevino, R., Zueras, P., & Turu, A. (2020). Living Alone over the Life Course: Cross-National Variations on an Emerging Issue. Population and Development Review, 46 (1), 169–189.

Quintano, C. and D'Agostino, A. (2006), Studying Inequality in Income Distribution of Single-Person Households in Four Developed Countries. Review of Income and Wealth, 52, 525-546.

Salvati, L., Serra, P., Bencardino, M., & Carlucci, M. (2019). Re-urbanizing the European City: A Multivariate Analysis of Population Dynamics during Expansion and Recession Times. European Journal of Population, 35 (1), 1–28.

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