The Creative Tank network has developed two benchmarking indexes - the Mailing Effectiveness Index (MEI) number and the List Quality Index (LQI) number - that enable e-newsletter publishers to compare the performance of their e-newsletters against the entire Creative Tank client database. The MEI gauges the success and effectiveness of a particular mailing based on open, click-through, unsubscribe, referral and spam complaint rates. The List Quality Index (LQI) score measures the cumulative performance of a list based on opens, bounces and Spam complaints.