Methods and devices for determining a number of mobile devices travelling from a first location to a second location are disclosed. A method includes determining a first subset of mobile location records associated with the first location, determining mobile device identifiers associated with the first subset, and modifying mobile location records in the first subset by replacing a mobile device identifier contained in each mobile location record with a new identifier of the first subset. The method may then determine a second subset of mobile location records associated with the second location, modify mobile location records in the second subset by replacing a mobile device identifier contained in each mobile location record with a new identifier of the first subset, and determine a number of mobile devices that travelled from the first location to the second location based upon the new identifier of the first subset.