Depends what you call an "author". If you extend the definition to include anyone who describes themselves as an author, even if they are fifteen years old and their latest "book" is 30 pages of plot-free dross about adolescent vampires, wizards, or their super-charged self being a popular heroic success at everything they try, then it's so close to zero that statistically it's not worth your while even opening up Word.
Most grown-ups who call themselves authors have been published, but usually not the way you might think. Often they write a column for their local paper or a magazine or some other kind of non-fiction writing, or maybe the odd short story here and there (also in a throwaway magazine) while dreaming of getting their actual book published one day.
A friend of mine recently had to describe a gilt-encrusted candle in 150 words, for a catalogue selling cheap tat like gilt-encrusted candles to people with more money than sense. He got a 2:1 in English, and that's what he's ended up doing.
Sensible advice is not to give up your day-job until you have actually had a book published and it's sold well and got good reviews. Until then, enjoy writing as a hobby.