Online retailers are increasingly using third-party online marketplaces (e.g., Amazon, Taobao) as an alternative sales channel to their website. While cross-channel sales elasticities have been established for many sales channel combinations (e.g., adding bricks to clicks), we lack an understanding of whether the use of third-party marketplaces grows or cannibalizes a retailer's sales. Practitioners argue that firms can build their e-commerce business through acquiring customers by selling on the marketplace. Indeed, a marketplace could complement a retailer's offering (e.g., acquiring new customer segments), although inventory effects might mitigate this complementarity. Alternatively, cannibalization might occur from losing customers from one's website to the online marketplace. The present research investigates which of the two opposing forces prevails using a time series of category sales data from one of the largest global marketplace sellers. The authors use vector autoregressive modeling to show that marketplace sales increase sales on a retailer's website (0.014% for every 1% in marketplace sales). This effect is strongest for categories with large choice and low product prices. Acquiring customers through the marketplace might be cheaper than through other sources (estimated at 24% of initial sales). However, online retailers should be aware that this strategy strengthens the marketplace and may have potential negative long-term consequences (e.g., through marketplace control of the customer relationship).

在线零售商越来越多地使用第三方在线市场（例如亚马逊、淘宝）作为其网站的替代销售渠道。虽然已经为许多销售渠道组合（例如，增加点击次数）建立了跨渠道销售弹性，但我们对第三方市场的使用是否会增加或蚕食零售商的销售额缺乏了解。从业者认为，公司可以通过在市场上销售来获取客户来建立电子商务业务。事实上，市场可以补充零售商的产品（例如，获取新的客户群），尽管库存效应可能会削弱这种互补性。或者，蚕食可能会因客户从网站流失到在线市场而发生。本研究使用来自全球最大市场卖家之一的类别销售数据的时间序列来调查两种对立力量中的哪一种占优势。作者使用向量自回归模型来表明市场销售额增加了零售商网站上的销售额（市场销售额每增加 1% 为 0.014%）。对于选择多且产品价格低的类别，这种影响最为明显。通过市场获取客户可能比通过其他渠道获取客户便宜（估计占初始销售额的 24%）。然而，在线零售商应该意识到这种策略会加强市场并可能产生潜在的长期负面后果（例如，通过市场对客户关系的控制）。