Visualizing spatial disparities in population aging in the Seoul Metropolitan Area

Populations are aging more and more around the world. The number of elderly people (age 65 and over) is expected to double from 703 million in 2019 to 1.5 billion by 2050 (UN, 2019). This phenomenon is amplified by continual improvements in health care services, which have extended life expectancy. However, the working-age population between 15 and 64 years old is gradually declining in step with the declining fertility rate. As a result, the old-age dependency ratio, which is measured by dividing the elderly population by the working-age population of one hundred people, is projected to increase incrementally worldwide. The United Nations (UN) projects that the old-age dependency ratio will increase globally from 11.7 in 2010 to 18.0 in 2030, and further up to 25.2 in 2050 (UN, 2017). Such a sharp increase in the old-age dependency ratio can become a serious social problem because it imposes on younger generations the great financial burden of increasing social welfare expenditures for older generations (Hu and Yang, 2012).

As population aging takes place at a fast pace in Asia, Korea is one of the top countries where the proportion of the elderly population is significantly high relative to the working-age population (UN, 2019). According to the UN's projections, the old-age dependency ratio in Korea is expected to reach 66.3 by 2050, while in the U.S.A. it will reach 36.4, in Sweden 41.3, China 44.0, and France 46.5 (UN, 2017). However, these differences occur not only among countries, but also within countries, as population aging tracks with spatial inequalities in socio-economic development (Cheng et al., 2018). Some regions in which farming or fishing are majority economic activities accommodate a large number of elderly people, but there is little influx in those places of individuals from younger generations. Such differences in net migration between rural and urban areas further exacerbate the spatial disparities in population aging.

Although local demographic decline transitioning has been a key issue in the field of urban and regional planning, there have been few attempts to measure regional differences in population aging with regard to spatial size and population density. To fill this lacuna, this paper aims to empirically visualize the spatial disparities of the old-age dependency ratio, taking Seoul Metropolitan Area as a case region. The SMA, where the capital of Korea is located, accounts for around 10% (11,851 km²) of the nation’s total area but more than half of the nation’s population (25 million). To visualize the changing patterns in spatial disparities of population aging over the past two decades, I use the most fine-grained block-level demographic data in SMA (Yang et al., 2016). The SMA holds 50,588 tracts, with each tract housing approximately 500 residents.

For the empirical period examined between 2000 and 2018, the overall old-age dependency ratio significantly increased from 7.669 in 2000 to 16.880 in 2018 (KOSIS, 2020). Figure 1 shows the surge of old-age dependency ratio in rings drawn from Seoul to the outskirts of the rural areas. Two decades later, the spread of the aging society emerged in most areas, excluding areas where new city developments were launched, such as ‘Paju’, ‘Songdo’, and ‘Dongtan,’ to name a few. Also, the speed of the increase in the old-age dependency ratio appeared greater in the outskirts of the SMA, including the coastal areas. Figure 2 shows cartograms that help visualize the spatial information considering the size of the variable value itself, rather than the size of each area (Gastner and Newman, 2004; Li and Sun, 2018). As the population is largely concentrated in Seoul, the 2000 visualization reveals that the old-age dependency ratio shows a low value (i.e. ten or less) in most areas. In fact, the population in Seoul accounted for 9.85 million in 2000 and 9.67 million in 2018, which makes up around 40% of the total population in SMA. Over the past several decades, the old-age dependency ratio has been growing at a brisk rate, especially in sparsely-populated rural areas. This paper suggests that it is time for urban and regional planners to have more discussions around providing sustainable public services and managing the issue of population extinction in areas experiencing a surge in the old-age dependency ratio. OPEN IN VIEWER

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Figure 2.

Cartograms of the old-age dependency ratio in SMA.