TCP Efficiency on Layer 4 Truespeed

How do you interpret the TCP Efficiency results on a Layer 4 Truespeed test? How is it calculated?

TCP Efficiency reflects how the TCP transfer is affected by retransmissions (a normal part of TCP transfer). The value is calculated by taking the number of transmitted bytes minus the retransmitted bytes divided by the transmitted bytes multipled by 100. A perfect value would be 100% indicating no retranmissions occurred.  When there are retransmissions and buffer delay is high then congestion is the most likely cause. When there are retransmissions and buffer delay is low then policy enforcement (policing) is the more likely cause.