A method for obfuscating granular transaction data via the introduction of noise includes: storing transaction data entries, each including transaction data values including at least a transaction amount and merchant identifier; receiving a data request including selection criteria and desired metrics; identifying a subset of transaction data entries based on the selection criteria; identifying a metric value for each desired metric based on the corresponding transaction data value in each of the transaction data entries in the subset; inserting noise to modify the subset by (i) adjusting the transaction data values included in at least two of the transaction data entries, and/or (ii) adding at least one transaction data entry to and removing at least one transaction data entry from the subset, where the inserted noise adjusts the metric values within a predetermined range; and transmitting the modified subset.