而基於expected risk premium (同 volatility?) 應該係會隨時間改變(例如 10 years rolling period),咁冇理由我嘅 efficient frontier (and therefore highest Sharpe ratio AA)唔會一齊隨時間改變,至少個邏輯上我覺得DAA係冇問題嘅
expected risk premium 同 CAPE ratio 學術上都應該幾 well documented. 基於 value spread 而買多啲 value stock 嘅做法都見幾多人講

1. 我唔知咁做會唔會 on average 唔同策略都有outperformance
2. 就算 on average 有outperformance,個premium會唔會好視乎你用咩策略,容唔容易overfit
3. 扣埋behaviour risk, time cost 同 trading cost 之後仲值唔值
以上三樣嘢我都未知