Nope, no compression on ADSL.
BT use packet shaping on their network and may also be serving up data from proxies they host.
Therefore for a given time period, the data transferred may be different as your traffic throughput gets artificially skewed by their network systems.
Also, are you counting the router throughput or your wifi throughput ? It may well be you're picking up non-internet traffic (e.g. sending files to print) if you're counting the wrong thing.
Last edited by mixture; 31st Dec 2012 at 13:36.