Eric von Hippel's 1986 paper explores the phenomenon of informal know-how trading between rival and non-rival firms, particularly in the US steel minimill industry. He argues that this form of cooperative R&D is a novel and economically sensible practice, even though it may seem counterintuitive given the competitive nature of such interactions. Informal know-how trading involves the exchange of proprietary technical knowledge between engineers in different firms, often through informal networks. This behavior is not always economically rational from a firm's perspective, but it can be in the long-term interest of firms to engage in such trading, especially when the knowledge is not vital to their competitive position. The paper presents a case study of the steel minimill industry, where firms frequently trade proprietary process know-how, even with direct competitors. This trading is often reciprocal, with firms sharing knowledge to gain competitive advantage. However, the trading is not always explicit, and firms may have different levels of secrecy and control over their know-how. The paper also discusses the economic rationale for such trading, using a "Prisoner's Dilemma" framework to analyze the incentives and outcomes of such exchanges. Informal know-how trading is contrasted with more formal forms of R&D cooperation, such as joint research agreements or licensing. It is argued that informal trading is more flexible and less costly, and can be more effective in certain situations. The paper also suggests that informal know-how trading may be applicable beyond the steel industry, in various other contexts where proprietary knowledge is a competitive advantage. The study highlights the importance of understanding the dynamics of such trading, as it can have significant implications for innovation, competition, and the overall efficiency of R&D processes.Eric von Hippel's 1986 paper explores the phenomenon of informal know-how trading between rival and non-rival firms, particularly in the US steel minimill industry. He argues that this form of cooperative R&D is a novel and economically sensible practice, even though it may seem counterintuitive given the competitive nature of such interactions. Informal know-how trading involves the exchange of proprietary technical knowledge between engineers in different firms, often through informal networks. This behavior is not always economically rational from a firm's perspective, but it can be in the long-term interest of firms to engage in such trading, especially when the knowledge is not vital to their competitive position. The paper presents a case study of the steel minimill industry, where firms frequently trade proprietary process know-how, even with direct competitors. This trading is often reciprocal, with firms sharing knowledge to gain competitive advantage. However, the trading is not always explicit, and firms may have different levels of secrecy and control over their know-how. The paper also discusses the economic rationale for such trading, using a "Prisoner's Dilemma" framework to analyze the incentives and outcomes of such exchanges. Informal know-how trading is contrasted with more formal forms of R&D cooperation, such as joint research agreements or licensing. It is argued that informal trading is more flexible and less costly, and can be more effective in certain situations. The paper also suggests that informal know-how trading may be applicable beyond the steel industry, in various other contexts where proprietary knowledge is a competitive advantage. The study highlights the importance of understanding the dynamics of such trading, as it can have significant implications for innovation, competition, and the overall efficiency of R&D processes.