## 6 Comparison of Basic Statistics  
In this section, we explain the outcomes obtained from the exploratory analysis in Table 4, which focuses on the impact of the HSR on mobile population growth at individual stations. The table shows the differences in mobile population recorded at each HSR station according to gender and age group. For example, Jeongeup city has a total of 172,597 (weekday average) mobile population records and the data observed at station is 13,117 which is about 7.6% of city total. Of 13,117, the number of records for age group of 60 is 2476 (18.9%) at before the opening of HSR. Moreover, the total records of city increase as 178,120 (+3.2%), but the number of over 60 is decreased as 1603 after the opening of HSR. The number differences are only presented in Table 4.  
Overall, the mobile population increased at all four cities during the weekdays, and the growth is shown to increase with the travel distance from Seoul. However, the mobile population and growth on weekends at Seoul are seen to decrease because of the decrease in the number of people over the age of 40. Interestingly, the HSR line was found to attract more people, especially the older people, to local cities than to Seoul. We would expect that the HSR stations at local cities form new hotspots due to the development of multi-functional facilities at the station periphery. Figure 2: Example of the selected mobile phone centroid of p-cell data within Seoul St.  
Mokpo, the outermost city from Seoul, has seen an increased mobile population growth for all age groups, with an almost 50% growth during the weekdays and over 60% during the weekends. This result shows that we can expect the people in Mokpo city to largely benefit from HSR installation. Figure 3 shows the box-plot of access distance range of mobile population. The box-plot represents the ranges of access distance to reach HSR station. We expect that if someone benefits with a short travelling time by using the HSR, then he/she would access an HSR station even if he/she resided far away from the HSR station. Therefore, Iksan and Mokpo stations were determined to have wider spectra of access distance after the launch of the HSR as the lower-and-upper quartile ranged wider compared to before condition. This illustrates that HSR attracts more people from a distance of approximately 10-15 km to 10-22 km at both stations. Jeongeup station shows an increase in the median access distance, although the access distance range is slightly decreased. Thus, the access distance range may vary depending on the city size, socio-demographic characteristics, and income level, etc. These results show that the HSR attracted more people living in widely from the area near the station, while the range of lower-and-upper quantiles varies at stations. This is especially true for Jeongeup, which is the smallest city along the HSR line with a population of approximately 114,000, consisting of over 30% of the age group of 60. However, it is difficult to determine the reason of decrease in the access distance at Jeongeup station. In contrast, Seoul station shows similar lower-and-upper quantile range of access distance although the median distance is barely increased. Therefore, we understand that the opening of the HSR had a relatively small effect on the mega city in terms of access distance range.