Dunno about any standard, but for me it differs depending on the type. My road bike with brifters has them darn near flat, as though they are extensions of the top of the bar. When I was setting up my touring bike, I found that I liked them tilted up a good bit because they aren't as beefy as the brifters and don't feel as good flat. Then again, the difference in handlebars and geometry between the two bikes may have something to do with it too.