Upstream, Downstream: Diffusion and Impacts of the Universal Product Code
研究了1975至1992年间通用产品码（条形码）的采用、扩散及其影响，发现网络效应推动扩散，采用后企业规模和商标注册增加，国内采用还提升了行业进口渗透率，表明条形码技术促进了产品创新和国际零售供应链发展。
We study the adoption, diffusion, and impacts of the Universal Product Code (UPC) between 1975 and 1992, during the initial years of the bar code system. We find evidence of network effects in the diffusion process. Matched-sample difference-in-differences estimates show that firm size and trademark registrations increase following UPC adoption by manufacturers. Industry-level import penetration also increases with domestic UPC adoption. Our findings suggest that bar codes, scanning, and related technologies helped stimulate variety-enhancing product innovation and encourage the growth of international retail supply chains.