The scrub rate is the percentage of leads that were not purchased by the Advertiser. If 100 leads were generated but only 80 were bought, the scrub rate was 20%. These are leads that didn’t make it through the Advertiser’s acquisition process – so they were scrubbed out. These are typically leads that are rejected in real-time because they didn’t meet the criteria of the lead buyer (also referred to as lead scrubbing). The higher the scrub rate the lower the effective CPL.