Alot depends on what you call keepers. I have 4 levels of keepers...
1) Good enough that little to no tweaking is needed, focus is excellent, exposure is perfect, suitable for large wall prints...1-2%
2) Composition isn't exactly right but can be fixed with a tiny bit of cropping, minimal tweaking required, suitable for med/lg prints....10-15%
3) Decent shot with some manipulation needed (backscatter removal, brightness/contrast adjustment), suitable for small prints....30-40%
4) Snapshot quality, usually kept for sentimental reasons or it's the only shot of something and is kept until a better one is taken (usually fish portraits), rarely printed and kept on file....10%
The rest is junk, fish butts, out of focus, over/underexposed, etc.
I seldom, if ever, adjust the color of my photos, although I know lots of folks do it. I like the colors to be natural to what I saw, not what I think they should be or what I think might make the photo better. It is what it is sort of thing. If a photo is properly exposed you shouldn't need to change the colors. At some point, with all the different ways a photo can be manipulated, it ceases to be a photo and becomes artwork. That doesn't make it bad/wrong, that's just where I, personally, draw the line.
Probably more than you wanted to know, right?