Unveiling the Dynamics of Irregular Migration and Border Mission Expenditures at the Serbian - Romanian Frontier: A Wavelet-Based Approach

Abstract

This study examines the dynamic relationship between irregular and smuggled migration flows and border mission expenditures at the Serbian - Romanian frontier using wavelet methods, over January 2018 to April 2025. Baseline wavelet analyses reveal that the interactions between migration flows and border mission expenditures are predominantly short-run, high-frequency and time-varying, with no evidence of persistent long-run relationships. The results identify clear lead-lag patterns, showing that sudden increases in irregular and smuggled migration are typically followed by higher border mission expenditures, reflecting reactive policy responses, whereas increased expenditures subsequently contribute to reducing migration flows, indicating a corrective feedback mechanism. Medium-run interactions are also observed, particularly for smuggled migration, suggesting that structural policy interventions gradually influence migration dynamics.  Robustness checks using wavelet cohesion and partial wavelet coherency confirm the stability of these dynamic relationships while highlighting the moderating effects of geopolitical shocks, economic uncertainty, regulatory changes and weather conditions. These findings support the adoption of a multi-horizon policy strategy that combines rapid operational responses, medium-term adaptive resource allocation and strengthened transnational cooperation to combat migrant smuggling. Future research should extend the analysis to multiple border regions using disaggregated data and complementary causal approaches.