我唔係講孖展利息,我就係講緊volatility drag, 跌完10%要升返11%嗰個,可能我哋定義唔同
我係咁樣定義
leveraged geometric mean = leverage ratio*arithmetic mean - volatility drag = arithmetic mean - (leverage ratio*volatility)^2 / 2
假設yearly normal distribution (我知實際唔係但close enough la),arithmetic mean return 7%, 一個波動15%,另一個10%,simulate一共一萬個一百年嘅portfolio,如下圖
如果計geometric mean return 嘅話(stay in the market就應該計呢個),明顯即使一樣arithmetic return ,波動高啲嘅嗰個組合geometric return 都會低啲。
所以開槓桿除咗放大咗個回報,仲放大咗個波動,而因為個volatility drag係計槓桿倍數嘅square,貿貿然開槓桿嘅話會令到Sharpe ratio比預期低。呢一點係無論你用咩工具做槓桿都會有
利申假設零成本無限rebalancing 去維持槓桿比例,槓桿ETF要 daily reset leverage 焗住高買低賣會再增加volatility drag,我諗呢個係你講緊嘅drag
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