Parking Lights

Hi I have a 92 jeep cherokee. For some unknown reason my rear parking lights do not work. The front ones work all my turn sugnals work, brake lights etc but the rear running lights do not work does anyone have any idea what it could be please let me know. Im very concerned i dont know what is wrong. It is the left and right parking light, and the license plate ;amp, the bulbs are fine, and wiring is fine could it be the switch why would the front ones work and not the back ones please help!!!!!!