Most of the webmaster in the forex industry should follow the traffic statistics of fxstreet (I do since 3 years). Francesc gives detailled stats each month. It’s a nice benchmark for me. I don’t worry about strong drop or growth in the number of visitors if Fxstreet have the same variation.
Since the beginning of this year Google adplanner seems to give not bad data for the number of visits. I will publish some data every month to follow the evolution of the forex’s audience.
You have to take care with those data because Google use several approximations… But it could be a nice benchmark because every website have the same approximations.