For a long time, there are two theoretical systems in risk measurement, they are full domain risk theory and asymmetric risk theory. In full domain risk theory, risk is defined as the uncertainty of returns.
長期以來，有關證券的風險度量存在著兩大理論體系——全域風險理論和非對稱風險理論： 全域風險理論將風險定義為收益的不確定性。