The digital economy and marine new-quality productivity: unraveling the N-shaped relationship

IntroductionMarine new-quality productivity (MNQP) has emerged as a critical driver for the high-quality development of China's marine economy, yet its relationship with the digital economy remains poorly understood.MethodsUsing panel data from 11 coastal provinces in China spanning 2011 -2021, this study constructs a comprehensive evaluation framework for MNQP and employs fixed-effects models, instrumental variable methods, and nonlinear regression techniques to systematically examine the impact of the digital economy on MNQP.Results and discussionThe findings reveal a significant N-shaped nonlinear relationship, indicating that as the digital economy develops, its marginal effect on MNQP exhibits an N-shaped pattern, with positive effects at low levels, negative effects at intermediate levels, and a tentative reversal at higher levels that warrants cautious interpretation. The turning points occur at digital economy indices of approximately 0.198 and 0.618. Benchmark regressions show a significant negative linear effect overall, while grouped regressions reveal positive effects at low levels of digital development and negative effects at high levels. Endogeneity and robustness tests confirm the reliability of these findings. Among control variables, regional economic scale and financial deepening exert significant positive effects, whereas trade openness shows an inhibitory effect. This study provides new empirical evidence on the complex nonlinear dynamics between the digital economy and MNQP, offering actionable policy implications for coastal regions at different stages of digital development.