하네다 공항 국제선 운항 재개가 나리타 공항 여객 수송량에 미친 영향 연구: 이중차분법 및 합성통제법 접근

초록

This paper examines the causal effects of Haneda Airport's resumption of international services (2010) and slot expansion (2014) on international passenger demand at Narita Airport, using a difference-in-differences (DiD) framework supplemented by the synthetic control method (SCM). Unlike previous studies that relied on demand forecasting models and discrete choice models, this paper applies a two-way fixed effects (TWFE) DiD design. Using annual panel data from 21 Japanese international airports over the period 2005–2019, we designate Narita Airport as the treated unit and 20 non-metropolitan international airports as the control group. The DiD estimate for the 2010 resumption event is β = −0.5972 (p < 0.01), indicating an approximately 45% decline in Narita's international passenger volume relative to the control group. The estimate for the 2014 slot expansion is β = −0.6322 (p < 0.01), confirming an additional demand diversion effect; however, given the temporal proximity of the two events, this coefficient should be interpreted as an incremental effect on top of the already-realized 2010 effect. The synthetic control method yields an average treatment effect on the treated (ATT) of −0.6927 for the 2010 event, consistent in sign and magnitude with the DiD estimate, thereby corroborating the robustness of the findings. An event study design supports the parallel trends assumption in the pre-treatment period (Wald F = 1.015, p = 0.429), and the post-treatment coefficients expand progressively from β = −0.217 in 2010 to −0.95 ~ −1.07 in 2017–2019, suggesting a cumulative demand diversion effect as Haneda's international capacity was continuously strengthened. Robustness checks including Leave-One-Out analysis and placebo tests confirm the stability of the estimates. While Wild Cluster Bootstrap and Randomization Inference yield non-significant p-values (WCB: 0.443 and 0.439; RI: 0.238 for both events), this outcome is attributable to the structural limitation of a single treated cluster rather than an absence of demand diversion effects. This paper provides quasi-experimental evidence on demand diversion within the Tokyo multi-airport system, and offers policy implications for cities managing comparable multi-airport systems, including Seoul, Beijing, and London.

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