Some of the information you include in your Requests for Proposal should be comparative benchmarks. Especially if your legal department wants to find a firm that will handle the services you need on a fixed fee, you want to provide and set some performance measures. Sometimes, you can provide benchmarks such as cycle time, disposition costs (defense vs. indemnification costs), charges dismissed, and discovery fees.
More commonly, tell the firms about your average number of cases (or whatever types of matters you cover in the RFP). Tell them about the number of firms you have retained and the broad strokes of your spend. If you can express workload in metrics, they will feel more comfortable with their proposals and will have better targets to shoot for. Metrics give RFPs texture and reality; comparative metrics give them crunchiness.