First of all, you did an absolutely awesome job. Very commendable.
How many airbases from the list were not in hi-res on the GE? We should also extend this project as soon as new airbase is available in hires, mark them on a map, maybe even make a placeholder layer for GE with all the bases' locations.
As for numbers of planes found - that is of course very inconclusive. All the reasons you offered are valid ones, i'd also like to add to them the numbers of airbases left unseen, the possibility of some planes being in the air (or even visiting some other airbase - maybe we saw some planes twice
) as a pic was taken.
I don't believe most images are years old though. Google earth itself, with its launch, increased the usage of spy pics for commercial purposes, people buying them left and right.
anyhow, some discrepancies between numbers seen here and and confirmed/lowest possible estimate numbers are really high.
There are 300 flankers in china, maps show just 21, that's 93% missing.
There are 136 j8s showing, out of at least 300 out there, more than 50% missing.
There's 164 j7eg showing, out of at least 300 out there, little less than 50% missing.
222 j7 showing, out of at least 400-500 out there, again some 50% missing.
just 7 jh7 shwing, out of at least 50 out there, at least 86% missing.
129 q5 showing, out of at least 300 out there, little more than 50% missing.
95 h6 showing for best percentage yet, though not too surprising considering their size, they're hard to hide.
What surprised me are h-5 which were said to be retired except for a testbed here or there.
I would also say it is very notable that most important new planes, flankers, j10, jh7 all have very low percentages showing. It is not beyond doubt that they are A) purposefully hidden or B) very much in use/training or combination of two.