TRAVELSIG,
My ratio is accurate as of June 2014.
Your odds are probably to do with your travel patterns. For example for the morning departures 0700-0930 you are looking at around 40% of flights by bus, but if you depart on the 1200-1500 flights almost all the flights at that time are by contact gate. On average over a 24 hr period It works out round the ratio I gave you.
Also there are certain destinations and routing patterns are more likely to get a contact gate or bus, for example if you fly to the US you will be getting a contact gate pretty much all the time. Alternatively if you fly every week MCT-DOH-TUN-DOH-MCT then almost all your flights will be by bus and you will have the impression that most flights are like that. Other examples are TK's flights to IST, they tend always get the contact gate even when there are other QR flights departing at the same time by bus.