How much of success is luck?

Several observations on this:

1) You make your own luck - for the most part - and that what we call 'being lucky' is a skill you can learn. See here for the research on this: http://www.psy.herts.ac.uk/wiseman/research/luckmain.html

2) The Andy Grove/ Einstein thing, of trying, striving, working really hard and trying to strategically place yourself in the 'right place' will eventually pay off, one way or another. This is essentially what the article adresses. This is a different kind of luck though.

3) Apart from personal 'luckiness' and hard work paying off, there are also occasional black and white swans - large random external events which affect peoples lives in good or bad ways. These are unpredictable and outside your control. Nassim Nicholas Taleb has a (quite hideous) website about this kind of thing: http://www.fooledbyrandomness.com/ He may also have written a popular book.

90%, and 10% very hard work, usually starting somewhere in your teens until you reach it.

If the above rule does not apply then it's 100% luck.

IMO the bigger the success, the bigger the influence of luck. If you have a good idea, are talented and work hard, then you're very unlikely to fail completely. But no amount of good ideas, talent or hard work can ensure that you'll be the next Google.

Andy Grove has a wonderful notion of something he calls "earned luck". One needs luck to succeed, but you can't sit around waiting for it. I came across it in his biography by Richard Tedlow... a highly recommended read.