With the rise of the digital economy, many firms are enhancing product line flexibility (i.e., the ability to adjust product line length or depth) to better manage demand uncertainties brought about by disruptive technologies. Concurrently, the booming digital economy has widened the information gap in supply chains. Retailers/platforms can now gather more detailed data to predict demand, but such data remains unavailable to manufacturers. This article studies how a manufacturer’s product line flexibility influences a retailer’s incentive to voluntarily share private demand information. We show that upstream product line flexibility encourages a retailer to voluntarily share information when product substitutability is low and the product line extension fee is moderate. This insight challenges the conventional belief that retailers should keep demand information private to maintain an advantage over manufacturers. Our work is the first to suggest that upstream product line flexibility can significantly motivate retailer information sharing. Additionally, we show that, although a social planner might prefer to withhold demand information from the manufacturer in the absence of product line flexibility, sharing this information becomes preferable when the manufacturer can adjust the product line length. The retailer’s decision on information sharing can align with the social planner’s in such scenarios. Furthermore, we demonstrate that, given upstream product line flexibility, except when product substitutability is not sufficiently high and the product line extension fee is moderate, the retailer’s information sharing decision is unaffected by whether the manufacturer determines the product line design before or after demand is realized and shared accordingly.

Purpose: The purpose of this paper is to analyze manufacturers' production decisions and governments' low-carbon policies in the context of influencer spillover effects.Design/methodology/approach: This paper investigates the impact of the social influencer spillover effect on manufacturers' production decisions when they collaborate with intermediary platforms to sell products through marketplace or reseller modes. Game theory and static numerical comparison are used to analyze our models.Findings: Firstly, under low-carbon policies, the spillover effect does not always benefit manufacturer profits and changes non-monotonically with an increasing spillover effect. Secondly, in cases where there are both a carbon emission constraint and a spillover effect present, if either the manufacturer or intermediary platform holds a strong position, then marketplace mode benefits manufacturer profits. Thirdly, regardless of business mode used when environmental damage coefficient is high for products; government should implement cap-and-trade regulation to optimize social welfare while reducing manufacturers’ carbon emissions.Practical implications: This study offers theoretical and practical research support to assist manufacturers in optimizing production decisions for compliance with carbon emission limits, enhancing profits through the development of effective influencer marketing strategies, and providing strategies to mitigate carbon emissions and enhance social welfare while sustaining manufacturing activities.Originality/value: This paper addresses the limitations of prior research by examining how the social influencer spillover effect influences manufacturers' business mode choices under government low-carbon policies and analyzing the social welfare of different carbon emission restrictions when such spillovers occur. Our findings provide valuable insights for manufacturers in selecting optimal marketing strategies and business modes and decision-makers in implementing effective regulations.