Abstract: Methods, apparatus, systems and articles of manufacture to reduce a processing burden on a hardware processor estimating a number of actual mobile devices in a geographic region are disclosed. An example method includes accessing mobile device advertisement impression data. The mobile device impression data identifies manufacturers of corresponding mobile devices and respective device identifiers. At least two unique device identifiers of the impression data correspond to a same mobile device. A total number of unique device identifiers associated with a first manufacturer in the impression data is determined. A de-duplication ratio is accessed based on an identity of the first manufacturer. The de-duplication ratio is applied to the total number of unique device identifiers associated with the first manufacturer to estimate the number of actual mobile devices associated with the manufacturer.