Food Consumption Vulnerability in a Shrinking City: Panel Evidence from Busan, South Korea

In many cities around the world, the map of daily life is changing. Neighborhoods that were once bustling with families and shops are slowly emptying out as people move away and grow older. This phenomenon, known as urban shrinkage, creates a unique challenge for city planners: how do you know if a neighborhood is truly struggling to get food, or if it simply looks quiet on a map? Traditional ways of measuring food access often rely on counting grocery stores and calculating driving distances. While useful, these methods only show where shops exist, not how people actually use them. A street might have a supermarket nearby, but if the residents are too elderly to walk there or if the store has closed its doors, the distance number tells a misleading story. To understand the real health of a community's food supply, researchers need to look at the actual flow of money and goods, watching how people shop in real time rather than just counting the buildings they pass.

This is the puzzle that researchers Namhoon Kim and Sanghyo Kim set out to solve in Busan, South Korea's second-largest city. Busan is a place where the population has been shrinking for decades, dropping from nearly 3.7 million people in 2000 to approximately 3.24 million in 2025, with nearly a quarter of its residents now aged 65 or older. The team wanted to move beyond simple maps of store locations and instead use a massive, detailed record of how people actually spend money. They gathered three years of monthly data from credit card transactions across 205 small neighborhoods in the city. By looking at the total amount of money spent, the number of times people swiped their cards, and the average size of each purchase, they could see the pulse of local food consumption. Crucially, they separated these records into two groups: transactions at stores that specialize in food, like grocery markets, and transactions at general retail stores that sell everything from clothes to food. This allowed them to see if a neighborhood was struggling with food specifically, or with shopping in general.

The researchers did not just look at the raw numbers; they used a statistical method to strip away the obvious reasons why some neighborhoods spend more than others, such as having more people or more stores. What remained were the hidden patterns of vulnerability. They found that low spending did not happen randomly. Instead, it clustered in specific areas, revealing three distinct types of struggling neighborhoods, each with a different cause and a different solution. The first type, which the researchers call "Both," represents the most severe case. These neighborhoods, concentrated in the old, historic core of Busan, are suffering from a double blow: the population is shrinking rapidly, and the small shops that remain are closing down. In these areas, the number of convenience stores and specialty food shops has dropped to between 13% and 43% of the levels in healthy neighborhoods. Here, the problem is a total collapse of both the people who need food and the places that sell it.

The second type, called "Food-only," tells a different story. In these neighborhoods, the shops are still there. The grocery stores and markets have not left. However, the people who live there have changed. The population has aged and shrunk, leaving behind many elderly residents who live alone. These residents are still buying food, but they are doing so less frequently and in smaller amounts, perhaps because they can only carry a few items at a time or because they live alone and buy less. In these areas, the physical supply of food is intact, but the demand has faded. The third type, "Retail-only," shows a neighborhood where the population is actually quite stable, but the small shops have disappeared. Here, people still live and work, but the local infrastructure has failed to keep up. They may be forced to travel further to find a place to buy basic goods, or they may be relying on larger stores that are not as convenient for daily needs.

The study suggests that treating all these struggling neighborhoods the same way would be a mistake. A policy that simply opens a new supermarket in a "Food-only" neighborhood might fail because the residents are already buying what they can, and the issue is not a lack of stores but a lack of mobility or support for the elderly. Conversely, building a welfare program in a "Retail-only" neighborhood might not solve the problem if the real issue is that no small shops are willing to open there. The most critical finding is that these patterns are not just random fluctuations; they are spatially clustered. The most vulnerable areas, where both people and shops are disappearing, are tightly packed in the old urban core of Busan. This concentration suggests that these neighborhoods are on a predictable path toward becoming "food deserts," a condition where residents have no reliable access to affordable, healthy food.

By using transaction data instead of just counting stores, the researchers have created a new kind of early warning system. They can spot these vulnerable patterns before a neighborhood becomes a complete food desert. The data shows that in the old parts of Busan, the decline is accelerating, with some neighborhoods retaining only about a quarter of the population they once had. The study does not claim to have solved the problem of food insecurity, but it provides a clear map of where the trouble is starting. It shows that in shrinking cities, the path to a food desert is not a single straight line but a series of different routes. Some neighborhoods lose their people first, others lose their shops, and the most dangerous places lose both at the same time. Understanding these differences is the first step toward fixing them, ensuring that interventions are targeted to the specific needs of each community rather than applying a one-size-fits-all solution to a complex and changing landscape.