A product catalog system includes a product catalog having product offers received from various merchants. The product catalog system includes an analysis module that determines, for each merchant that provides product offers, which product offers are for products that are likely to be variants of one another based in part on titles of the products and assigns sets of product offers that are likely to be variants a merchant cluster identifier. The analysis module groups the product offers into product catalog entries based on the particular product that the offers are for. The analysis module determines which products are variants based on associations between the product catalog entries and the merchant cluster identifiers of the product offers included in the product catalog entries.