"Andy Warhol said everyone will be famous for fifteen minutes".
"Well how can everyone be famous for 15 minutes there's not enough time in the world"
There are approximately 2,452,800 fifteen-minute slots in a 70-year lifetime (70*365*24*4).
7.9 billion people (well, in the time it takes me to do the sums).
7,900,000,000 / 2,452,800 = 3221.
So there would be over 3000 famous people at any given time.
There could well be 3000 celebrities at a given level of fame. So Warhol was probably spot on in his calculations. Depending on how well known you have to be considered famous.