Retail e-commerce (B2C - business-to-customer) grows more in developing markets than in developed ones, however, most studies in the area were aimed at developed markets. This thesis aimed to compare the relative efficiency of publicly traded companies that operate in the retail of physical products online in a developed market (Canada) and another in development (Brazil), separately, and to discuss the practices of each market. To this end, a new instrumental approach was proposed, based on an integrated model of Data Envelopment Analysis (DEA) and Optimal Control Theory (OCT) to measure the efficiency of total inventory costs, based on the theory lean management, integrating the concept of capacity efficiency (i.e., management of physical assets). Also, the model directly incorporated inflation and, indirectly, the gross margin. The model was applied to public data from two sets of companies classified as Retail (Var) or Non-Durable Clothing and Consumer Goods (VBCnD) - one composed of 12 Canadian companies (CA) and another by 17 Brazilian companies (BR) -, during the period from 2016 to 2019. Then, a qualitative analysis of the B2C of the companies was made. The results showed that, in both countries, Var companies were more efficient than VBCnD. There are indications that BR companies were at a more advanced stage of the digital transition. In Brazil, Var companies prioritized sales by app and marketplace (own or third parties) and VBCnD companies, by app and virtual store. In Canada, Var companies have prioritized virtual stores and apps, while VBCnD, marketplaces (third parties), and apps. Although it is a common practice for BR Var companies, no observed CA company controls a marketplace. In Brazil, there was a strategy in which two companies operated in parallel, one specialized in B2C and the other in physical retail, though they were not more efficient than the market. The results pointed to BR companies Magazine Luiza, Arezzo, Estrela, and Via Varejo as market benchmarks, so their best practices should be studied.