Various systems for collecting individual post-sale market data for products or services, and determining aggregate post-sale market data therefrom, are provided. In such systems, a sale of a product or service may trigger a third party, such as a payment provider, to arrange for the collection of individual post-sale market data from the consumer. Dependent upon the type of product or service involved, a schedule for continuously submitting post-sale market data for the product or service may be provided and the consumer may be encouraged to submit post-sale market data in accordance therewith through a variety of incentives. The received, individual, post-sale market data may be aggregated by one or more sources to determine aggregate post-sale market data for the product or service. The submitted individual data and/or the determined aggregate post-sale market data may then be provided to consumers in order to assist them in making purchasing decisions.