Artificially inflating call volumes to a carrier that collects high access charges, typically by routing calls to free conference or chat lines, so the carrier can share the revenue.
Access stimulation takes advantage of intercarrier compensation. Certain local carriers charge long-distance carriers access fees to complete calls to their numbers. By partnering with services that attract large volumes of inbound calls, such as free conference bridges, those carriers generate a stream of access revenue, part of which is passed back to the partner.
The FCC adopted rules in 2011 to limit the practice and tightened them in 2019, shifting certain transport costs to the carrier engaged in access stimulation rather than the long-distance carrier delivering the calls. The rules define access stimulation using traffic ratio tests rather than banning any particular service outright.
In traffic data, pumping usually shows up as a heavy concentration of minutes terminating to a small number of rural exchanges, long average call durations, and inbound-to-outbound ratios far out of line with normal subscribers. Comparing a route against its own history, and against similar exchanges, makes these anomalies stand out even when the absolute volumes are modest.
Why it matters to carriers
Long-distance and wholesale carriers can end up paying significant access charges for traffic they never expected to carry. Monitoring termination by exchange and carrier, and knowing how the current FCC rules allocate costs, helps you dispute improper charges and decide which routes are worth carrying.