A method for outbound/inbound roaming market share estimation executed by an inter-operator carrier, wherein said inter-operator carrier is an interconnect facility that interconnects mobile communication networks, comprising estimation of the distribution of outbound roamers (300; 400) of a home mobile communication network over visited mobile communication networks (A1, A2, A3, B1, B2, B3, C1, C2, C3) in one or more geographical area (A, B, C), wherein said inter-operator carrier has a contract with at least one of said visited mobile communication networks (A1, A2, A3, B1, B2, B3, C1, C2, C3) to handle a percentage of its international traffic, said method comprising: a. maintaining frequent roamer information (RS1, RS2, RS3,...) for subscribers (S1, S2, S3,...) of said home mobile communication network comprising maintaining a frequent roamer score (RS1, RS2, RS3,...) for subscribers (S1, S2, S3,...) of said home mobile communication network and changing status of a subscriber for a predetermined time period from non-frequent roamer to frequent roamer when said frequent roamer score (RS1, RS2, RS3,...) exceeds a predetermined threshold; wherein the frequent roamer score for a subscriber is a number of roaming events of said subscriber; b. generating a sample set of frequent outbound roamers of said home mobile communication network; c. polling each mobile subscriber in said sample set of frequent outbound roamers with a location request, wherein a location request is a query message to the mobile subscriber requesting to reply with location details; d. analysing replies to said location request received from said sample set of frequent outbound roamers to determine therefrom geographical areas and visited mobile communication networks wherein said frequent outbound roamers of said sample set are located; e. determining a relative distribution of outbound roamers of said home mobile communication network across geographical areas (A, B, C) and/or visited mobile communication networks (A1, A2, A3, B1, B2, B3, C1, C2, C3) from analysis of said replies received as the percentage of frequent outbound roamers in said sample set of frequent outbound roamers located respectively in said geographical areas (A, B, C) and/or visited mobile communication networks (A1, A2, A3, B1, B2, B3, C1, C2, C3). a. maintaining frequent roamer information (RS1, RS2, RS3,...) for subscribers (S1, S2, S3,...) of said home mobile communication network comprising maintaining a frequent roamer score (RS1, RS2, RS3,...) for subscribers (S1, S2, S3,...) of said home mobile communication network and changing status of a subscriber for a predetermined time period from non-frequent roamer to frequent roamer when said frequent roamer score (RS1, RS2, RS3,...) exceeds a predetermined threshold; wherein the frequent roamer score for a subscriber is a number of roaming events of said subscriber; b. generating a sample set of frequent outbound roamers of said home mobile communication network; c. polling each mobile subscriber in said sample set of frequent outbound roamers with a location request, wherein a location request is a query message to the mobile subscriber requesting to reply with location details; d. analysing replies to said location request received from said sample set of frequent outbound roamers to determine therefrom geographical areas and visited mobile communication networks wherein said frequent outbound roamers of said sample set are located; e. determining a relative distribution of outbound roamers of said home mobile communication network across geographical areas (A, B, C) and/or visited mobile communication networks (A1, A2, A3, B1, B2, B3, C1, C2, C3) from analysis of said replies received as the percentage of frequent outbound roamers in said sample set of frequent outbound roamers located respectively in said geographical areas (A, B, C) and/or visited mobile communication networks (A1, A2, A3, B1, B2, B3, C1, C2, C3).