## 4 Analysis and Results
As with the abovementioned hypotheses, the interregional traffic volume, to a large extent, reflects the interregional socio-economic dependency, the positive relationship between the operation of KTX, and the dependency of other cities upon Seoul suggests that their urban functions may be absorbed to Seoul through the accumulation effect in the long run--that is, the potential straw effect would prevail over time. This finding is also consistent with [PERSON] (2011), who found that the construction of a highway network might lead to an asymmetric effect on local economic growth across cities in Korea, especially socioeconomically advantaged areas benefitting more from this improvement than those relatively lagging areas (Korea, 2015). Therefore, we can imply that Seoul could take advantage of the position of central city in terms of economics and culture to achieve utility differentials derived from these advantages after the KTX construction--besides these advantages may become increasingly significant over time due to the accumulation effect. In contrast, the local population and associated economic activities in a relatively developing area would potentially decrease as individuals put more emphasis on the accessibility to employment when choosing household location (Korea, 2015), then the straw effects occur. The results underscore the importance of making a comprehensive assessment on the costs and benefits of new HSR planning, particularly the regional disparity in terms of socioeconomic development. As HSR development exerts influence on resource allocation through improving the accessibility of cities that connect to the new transport network, accessibility has been an essential means to assess the potential accessible resources reached by transport within a certain distance (Korea, 2015; [PERSON] and [PERSON], 2016). [PERSON] and [PERSON] (2016) introduced market access into their research to reflect the changes in accessibility so as to examine the role that railway construction had played in American economic growth (Korea, 2015). Moreover, the attractiveness of potential destinations (e.g., employment, gross domestic product (GDP)) and the cost of reaching the destinations (e.g., travel time, generalized travel cost) are usually considered together when calculating the accessibility (Korea, 2015). Market access is capable of quantifying the overall impact of railway development, which provides a reference for us in analyzing the effect of KTX on the relative attraction of cities in Korea. We construct market access as below:  
\[MA_{o}=\sum\
olimits_{d=1}^{n}c_{\alpha d}^{-\theta}P_{d} \tag{3}\]  
where \(MA_{o}\) denotes the market access of city \(o\), \(c_{\alpha d}\) denotes the minimum commuting time from city \(o\) to city \(d\), \(\theta\) represents the elasticity of trade, \(P_{d}\) represents the market size of city \(d\) (GDP in this paper), and \(n\) denotes the number of cities. We used market access, calculated through ArcGIS 10.2, as the alternative independent variable to check the robustness of our main results. The improved accessibility of different geographic areas caused by new HSR constructions contributes to the exchanges of personal and information among them, particularly between areas that have been connected to the HSR network together. So, the changes in market access, attributable to new HSR constructions of a city, could function as an indicator to measure the level of HSR development. However, with the development of KTX, the market access of each city will be improved to a different degree, major cities may benefit more from it as their economic and cultural status enables them with more decision-making power over the planning and construction of new transport infrastructures, then acquiring a comparative advantage in the competition of attracting people. The results with market access as the key independent variable are shown in Table 5--across columns we find a similar pattern of coefficients, which provide additional support for our baseline results.