Climate change, geography and trade agreements: A perspective of Asian bilateral trade

PLOS One | https://doi.org/10.1371/journal.pone.0320363 April 25, 2025 16 / 23 PLOS One Trade agreement, climate change and geography reported in Table 7 for the robustness check. The replacement of the core gravity variable, distance, with a new measurement scale indicates the same results with the minor changes in magnitude as estimated in a simple regression. The remaining gravity variables do not change. Column (6) reports that all geographic variables are positive, with the exception of physical distance. Physical distance as a geographical factor has a high impact on exports. Export volume is highly affected because of the great magnitude of domestic and partner countries’ populations and GDPs. Columns 2 and 5 report the estimate of PPML. All geographical factors expect positive signs and are statistically more significant than domestic CO2. Domestic countries that have access to the Indian or the Pacific Oceans remain significantly negative compared with partner countries. The variable tariff imposed by domestic countries on trade policy has expected signs. The world’s GDP is found to be greater in magnitude in domestic geography than in partner countries’ geography. Table 7. Robustness Checks. Exporting Countries Importing Countries Estimation QREG PPML 2SLS New Variable PPML 2SLS (1) (2) (3) (4) (5) (6) VARIABLES Dependent Variable: Exports CO2 -0.325 -0.767*** 1.069 -0.327*** 0.259*** 7.399 (1.494) (0.073) (3.447) (0.048) (0.170) (21.410) Physical-distance 0.552*** 0.209*** 0.939 0.117*** 0.008*** -0.086

-0.325 (3.720) (0.878) (0.018) (8.970) (3.986) LnGDP 0.444*** 0.548*** 0.466 0.681*** 0.663*** 4.628 (0.055) (1.880) (0.800) (0.019) (9.180) (9.142) Lntariff -0.366*** – -0.032*** -0.023*** -0.018*** – (0.022) – (3.040) (0.003) (1.440) – Lndistance -1.023*** -0.712*** – – -0.634*** – (0.038) (7.240) – – (6.820) – Access to Ocean -0.004 – – 2.845*** – – (0.609) – – (0.040) – – Common border 2.381*** -0.179*** – 3.456*** 0.106*** – (0.109) (1.730) – (0.071) (1.750) – Lnpopulation 0.789*** 0.583*** – 0.182*** 0.0417*** – (0.233) (5.510) – (0.015) (5.240) – Lntotal distance – – – -0.302*** – – – – – (0.054) – – Lnworld GDP – – 707.1 * – – -3.065 – – (6.600) – – (6.573) Constant – – -22,418 * -6.808*** – 6.873 – – (13.521) (0.973) – (2.757) Observations 44436 44436 44436 44436 44436 44436 R-squared 0.405 0.104 – 0.328 – – Number of exporters – 46 – – 46 – Note: the term ***, ** and * denote that significance level at 1%, 5% and 10% respectively. Ln indicates logarithm for variables. https://doi.org/10.1371/journal.pone.0320363.t007