According to the standard formulation, stock prices tend to revert toward the present value of estimated future earnings (including growth in those earnings), discounted at the so-called “risk-free rate,” augmented by an equity risk premium. More precisely, the forward earnings yield – that is, the inverse of the P/E ratio – is equal to the risk-free rate plus the equity premium, minus the growth rate of earnings.
根据标准公式，股价总是趋向于估算未来盈利（包括这些盈利的增长）根据贴现而得的现值。贴现率为所谓的“无风险利率”加上一个股票风险溢价。更准确地说，前瞻盈利收益率——即市盈率的倒数——等于无风险利率加上股票风险溢价再减去盈利增长率。（当然，拜（比如）非理性繁荣、价值投资者所带来的暂时性下跌或时机不当的逆向投资交易所赐，市场路径是波折的。）