South Korea has experienced rapid economic development since the 1960s. However, pronounced regional disparities have concurrently emerged. Amid the escalating regional inequalities and persistent demographic challenges characterized by low fertility rates, regional decline has become a pressing issue. Therefore, the feasibility of expanding transportation networks as a countermeasure to regional decline has been proposed. This study utilizes the synthetic control method and spatial difference-in-differences methodologies to assess the impact of the 2017 opening of Seoul–Yangyang Expressway on economic development and population inflow within Hongcheon-gun, Inje-gun, and Yangyang-gun. The purpose of this study is to evaluate the effectiveness of highway development as a policy instrument to mitigate regional decline. Findings from the synthetic control method analysis suggest a positive impact of the opening of the expressway on Hongcheon-gun’s Gross Regional Domestic Product (GRDP) in 2018, as well as Yangyang-gun’s net migration rates from 2017 to 2019. Conversely, the spatial difference-in-differences analysis, designed to identify spillover effects, reveals negative impacts of the highway on the GRDP and net migration rates of adjacent regions. Consequently, although targeted transportation infrastructure development in key non Seoul Metropolitan cities may contribute to ameliorating regional imbalances, results indicate that such measures alone are unlikely to suffice in attracting population to small- and medium-sized cities outside the Seoul Metropolitan Area.

Sustainable innovation is crucial for addressing social and environmental challenges and is a key driver of enterprise competitiveness and economic growth. This study examines how board heterogeneity influences sustainable innovation in enterprises, particularly within the context of China’s Science and Technology innovation board. Findings reveal that diverse boards enhance sustainable innovation and impact M&A activities, which in turn mediate the relationship between board diversity and corporate sustainability. The research aims to understand the optimal board composition for scientific and creative enterprises, analyze the mechanisms behind board heterogeneity’s effect on innovation, and assess M&A’s role in this process. The study’s outcomes underscore the importance of board diversity for fostering sustainable innovation and suggest that M&A can be a critical pathway to enhancing corporate sustainability.