While this link will only show the user count history of Steam users on MWO I think it is close enough to the rule of large numbers to assume that if the Steam user count is high the general user count is high and vise versa. This can be useful in determining possible wait times for drops. Also the graph in this link shows the user count history for the last week. Other time frames are available ranging from 48 hours to one year.
MWO Users on Steam