did you ever have your tonsils or adenoids removed?
i have this problem often also. its just like your wife said. infact, i found that it was extremely worse when i smoked. as soon as i quit smoking, i quit coughing and clearing my throat all the time. sometimes ( mostly during the pollen seasons and other times when i am around allergens) i still do have to clear my throat a lot, and also find myself swallowing a lot because i feel like something is back there. it can get really annoying. it also does it when i get nervous, like i know i am about to talk to someone on the phone like a client or something. it is drainage though. you should either take an antihistamine or try to find your allergen and eliminate it.