From Marshall's external economies to external economies of transformation in contemporary industrial spaces.

This article focuses on the evolution and contemporary relevance of Alfred Marshall’s concept of external economies (EEs) as expressions of collective efficiency in industrial organisation and development. It traces three generations of external economies of development (EEDs): Marshall’s original EEDs observed in nineteenth-century industrial districts (IDs), the Marshallian EEDs (MEEDs) associated with twentieth-century local productive systems and flexible specialisation, and the newly proposed Marshallian external economies of transformation (MEETs) characterizing current industrial spaces facing disruptive green and digital transitions. MEETs extend traditional sources of collective efficiency by trespassing sectoral, societal, governance, and territorial boundaries, emphasizing cross-sectoral collaboration, diverse societal engagement, fluid multi-level governance, and multi-territorial networks. The article offers a systematic framework for understanding these evolving forms of EEs to inform research and policy on place-based industrial development and transformation.