Dr. Zaus
Lifer
Hard to quantify, but I would say my passive vocab is 10-15X larger than my active. Maybe more. Between my job (patent attorney) and my education (chem and law), I know an awful lot of legal, science, and technology terms. I've basically spent the last 13 years reading technical and legal journals and writing a new technical paper (a patent application) every 3-4 days. Have pretty good vocab in chemistry, biology, math, cryptography, software, optics, classic and quantum physics, some EE, materials science, etc., but I would not say I use those terms in everyday speech.
I was also a state spelling bee champion back in the 80's. That helps build passive vocab quite a bit.
there should be vocabulary Bees