E-commerce platforms, such as Amazon, Alibaba and Flipkart, that match sellers and consumers at an unprecedented scale, operate their internal search engines to help buyers find relevant products from a large number of sellers, and also allow sellers to advertise to consumers for positions in...

We study the optimal algorithm decisions of a platform on ranking products sold by sellers--who may use fake sales to boost the rankings of their products--and the impact on consumers and sellers. We design a model of an online retail marketplace with competing sellers. The platform decides...