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. Alternatively, such post-sale market data may be directly provided by smart devices and the like. 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. Individual post-sale market data may be normalized based on identifiable traits of the individual submitting the post-sale market data prior to such aggregation. 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. The collection and dissemination of post-sale market data may be accomplished, for example, via a software agent, such as a shopping bot, which may provide desired post-sale market data to a consumer prior to a sale and which may initiate collection of individual post-sale market data after a sale is recognized. Various other on-line and off-line embodiments are proposed for the collection, aggregation and dissemination of such post-sale market data.