Joinpoint regression as a monitoring tool for agrifood performance and trajectory changes in four certified Bierzo products 2000–2024

Although territorial quality systems and collective branding are widely used in European rural policy, quantitative evidence on long-run performance dynamics at product level remains limited. This study provides an exploratory assessment of temporal patterns in four certified agrifood products from El Bierzo (Spain)—Botillo, roasted pepper, Reineta apple, and Conference pear—over 2000–2024 (product-specific windows). Using Joinpoint (segmented) regression, we identify statistically significant changes in trajectories for turnover per unit/hectare and yield per hectare, and we describe how these breakpoints align in time with key institutional milestones, including the launch of the collective trademark Alimentos de Calidad del Bierzo in 2021. Results show heterogeneous dynamics across products: Botillo displays multiple turning points, with a strong rebound in 2001–2003 (APC up to + 6.29%) and moderate growth in 2003–2021 (APC + 0.18% to + 1.39%), followed by an acceleration after 2021. Roasted pepper shows turning points in both yield (2004; 2021) and turnover (2005; 2021), while apples and pears exhibit additional structural changes in the 2010s and early 2020s. These patterns are consistent with the view that certified products respond differently to market and production shocks, and that collective governance changes may coincide with shifts in economic trajectories. However, the design does not support causal attribution: breakpoints may also reflect exogenous factors such as price dynamics, climate variability, and post-pandemic market adjustments. Overall, the paper presents Joinpoint modelling as a useful tool for monitoring territorial quality systems and suggests that future research should combine trend analysis with contextual variables and comparative series.