14. A system for detecting fraud in health care transactions, each transaction including at least one service provided to a client by a provider, the system comprising: at least one data processor; and memory coupled to the at least one data processor, the memory storing instructions, which when executed, cause the at least one processor to perform operations comprising: retrieving co-occurrence data, the co-occurrence data indicating an historical likelihood that a client will receive both a first service and a second service, the co-occurrence data being based on a vector space modeling of historical service co-occurrence in which performed service codes are represented in a vector space derived from a statistical distribution of service codes in reimbursement claims; retrieving client historical data, the historical data including a plurality of historical services received by the client; for each of the plurality of historical services in the client historical data, determining from the co-occurrence data a likelihood of the provided service co-occurring with the historical service in order to determine an overall inconsistency metric; and responsive to the overall inconsistency metric exceeding a threshold, indicating that the transaction is potentially fraudulent.
15. The system of claim 14 , wherein determining the likelihood of the provided service co-occurring with the historical service in order to determine the overall inconsistency metric further comprises: determining for each combination of the provided service and a historical service received by the client, an inconsistency value; and determining a metric of the inconsistency values.