The rail utilisation strategies published by the Strategic Rail Authority contained information of a kind not replicated in later documents created by Network Rail. For instance, the 2005 West Midlands strategy included a breakdown of passenger arrivals at Birmingham New Street, by time of day.
Because of the existence of Silverlink, it was possible to see the relative (un)importance of both intercity and regional West Coast Main Line traffic at Birmingham New Street.
Most of the passenger volume was, and is, non-WCML and / or short distance. No doubt total volume has increased since the mid-noughties, but the proportions are probably much the same.