Abstract
Against the backdrop of the global marine economy's transition toward innovation-driven development, the selection of technological upgrading paths is a critical step for marine enterprises to achieve total factor productivity (TFP) improvement. Based on Chinese enterprise tax survey data from 2016 to 2020, this paper integrates independent research and development (R&D) and external equipment procurement into a unified analytical framework, using multiple econometric and causal identification models to systematically examine the internal mechanisms through which these dual technological paths drive TFP improvement in marine enterprises. The results indicate that both independent R&D and external equipment procurement significantly enhance the TFP of marine enterprises, exhibiting a substantial positive synergistic effect. Furthermore, the driving effects of these two paths on TFP are subject to dual threshold constraints related to enterprise resource boundaries. When an enterprise’s internal business diversification degree or external energy consumption intensity crosses critical thresholds, the marginal returns of technological output demonstrate a non-linear, regime-switching characteristic of structural decline. Finally, employing a multiply robust causal identification model, this paper reveals optimal strategic differentiation under capability heterogeneity constraints: the optimal decision-making of high-tech enterprises converges on a dual synergistic path, whereas non-high-tech enterprises, constrained by higher endogenous innovation costs, adopt the single path of external equipment procurement as their rational dominant strategy. This study enriches the micro-level empirical evidence regarding technological progress and productivity improvement in the marine industry, providing a theoretical reference for the formulation of differentiated innovation support policies.