One of the multiple providers of services is then selected by generating an access code corresponding to one of the service providers in accordance with a predetermined algorithm which provides a desired distribution of {HEAD ~ usage} by {TAIL ~ the subscriber} of a plurality of the service providers 
One of the multiple providers of services is then selected by generating an access code corresponding to one of the service providers in accordance with a predetermined algorithm which provides a desired distribution of { HEAD ~ usage } by { TAIL ~ the subscriber } of a plurality of the service providers
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