Fig. 3

Temporal changes in EWP and decomposition stages. This line chart depicts the annual variation trends of three key efficiency indicators in CCUA over the study period: overall Ecological Welfare Performance (EWP), ecological economic efficiency (Stage 1), and economic welfare efficiency (Stage 2). The vertical axis represents efficiency values (ranging from 0.55 to 0.95), and the horizontal axis represents the year (2012–2022). The chart shows that EWP fluctuated around 0.629 with an overall upward trend; ecological economic efficiency (average 0.843) was consistently higher than economic welfare efficiency (average 0.773).