The P/E ratio (price-to-earnings ratio) of a stock (also called its "P/E", or
simply "multiple") is a measure of the price paid for a share relative to the
annual net income or profit earned by the firm per share.
Important: This measure should not be used in production code if used
with Compustat data, since Compustat data may not lag accounting data to
account for delays in release. Thus it may contain data that was unavailable
at the time.
TODO: verify how the info release date from Compustat has been manipulated
(should be fixed/offset in Compustat class, not this)