Innovation efficiency and technology heterogeneity within China's new energy vehicle industry: A two-stage NSBM approach embedded in a three-hierarchy meta-frontier framework

Exploring innovation efficiency (IE) and technology heterogeneity within the new energy vehicle (NEV) industry is significant for advising industrial growth and healthy development. This paper embeds a two-stage network slacks-based measure (NSBM) approach into a three-hierarchy meta-frontier framework to evaluate the value chain's IE and the technology heterogeneity under the industrial chain structure. The observations were as follows. The industrial IE was low, particularly in the product creation stage, and the downstream IE ranked at the top, followed by the midstream and upstream. Furthermore, technological heterogeneities existed within the industry; the upstream technology level aligned with that of the industry, whereas the gaps between midstream, downstream, and industry were significant. Analogously, the battery enterprises' gap was minor upstream; nevertheless, the gaps between electric engine, electric control enterprises, and upstream were more pronounced. Additionally, management inefficiency contributed more to the industrial innovation inefficiency than the technology gaps inefficiency. Finally, industrial productivity declined sharply due to the technology gaps' change, except in battery enterprises. Our work will provide valuable insights for industrial policies' evaluation and improvement.