Latency decreases the total amount of bandwidth one singe TCP stream can use. The more latency, the lower the bandwidth. TCP Window Size also affects throughput.
Brad Hedlund has created a very good article with specific calculations.
http://bradhedlund.com/2008/12/19/how-to-calculate-tcp-throughput-for-long-distance-links/
The biggest misconception I hear is that the network is limiting Windows to 10Mbps when transferring files over a 100M WAN connection. One TCP Stream can only consume so much bandwidth depending on Window Size and Latency. Use a tool such as iPerf can test link throughput by pushing UDP packets that don't rely on TCP Window Sizing and latency.