US Patent 9324095 Determining conversion rates for on-line purchases

Identifying on-line advertising conversions includes identifying, at a computer server system, a plurality of reports from one or more computing devices, wherein each of the reports indicates a clock skew between one of the computing devices and a clock server system; using the clock skews to determine that two or more of the reports are likely from a common computing device; determining that the two or more of the reports are common, in that they correspond to display of an advertisement on the common computing device and to purchase of on-line content with the common computing device; and indicating that a purchase conversion occurred based on determining that the two or more of the reports are common.