I wonder about this. Does anyone have an idea what percentage of the VFR
airplanes carry a transponder detector, including the low cost units?
I'd guess a majority of them do, but I haven't seen any numbers. If so,
then a transponder would help you avoid (indirectly, since they would be
doing the actual "avoiding") the majority of VFR traffic.
Sailplane Operation" at www.motorglider.org



I fly a fair number of single engine VFR and IFR aircraft throughout
the year. My personal experience is that I have yet to flown one that
had any sort of Transponder Detector. I have talked to a couple pilots
that would like to get one, but have yet to actually do so. So my
personal experience is that very few VFR Single engine aircraft carry a
Transponder Detector. On the other hand very few of these aircraft fly
above 10,000 ft on a regular basis as well.

Brian Case
CFIIG/ASEL