D700 EV compensation question

I've shot a few thousand images with my D700 and have noticed that I consistently have to put in a +.3 EV compensation in order to get a balanced histogram. I shoot RAW exclusively and this is true for all ISO settings and independent of which lens I use. I normally shoot in aperture priority.

After some advice from Thom Hogan, I began shooting a UNIWB profile, but that still

Is this normal? Should I send the body to Nikon for exposure meter calibration? Or is this no big deal?

Thanks,
Mike