Known unknowns abound about the Saudi Aramco IPO expected this year on Saudi Arabia's' domestic exchange, including what the offer price will be and just how much of the company will be floated.
The big picture: Even still, the expected sale of just a tiny percentage of the company valued at well over a trillion dollars could be the biggest IPO in history.
Go deeper: New Aramco IPO prospectus touts strengths amid investor questions