Short-Term Associations Between a Government-Funded Sterilization Program for Owned Outdoor Dogs and Abandonment-Related Shelter Admissions in the Republic of Korea: A Nationwide Municipality-Level Panel Study

Sterilization programs for owned outdoor dogs aim to reduce uncontrolled breeding and subsequent abandonment, but population-level evidence remains limited. This study examined short-term associations between the Korean government-funded sterilization program introduced in 2022 and shelter-recorded abandoned-dog admissions using annual data from 229 municipalities from 2019 to 2024 (1374 municipality-year observations). The outcome was shelter-recorded abandoned-dog admissions per 100,000 residents. Socioeconomic associations, program implementation, and implementation volume were evaluated using two-way fixed-effects (TWFE) and difference-in-differences (DID) models. Estimates were interpreted as ecological associations because parallel pre-intervention trends could not be fully established, program allocation was non-random, and eligible owned outdoor dog populations were unavailable. In the primary linear TWFE models, neither program implementation nor implementation volume was significantly associated with the shelter-recorded abandoned-dog admissions, and urban–rural-stratified analyses yielded similar null findings. Baseline-need-scaled sensitivity analyses produced positive associations in the pooled and urban samples, indicating sensitivity to denominator choice and model specification. Province-specific analyses were heterogeneous but inconsistent. Overall, the analyses provided no consistent evidence of a short-term reduction associated with the program. Future evaluations should measure coverage among eligible owned outdoor dogs, use longer follow-up, and evaluate sterilization within broader dog population management.