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02-05 How hedge funds use the CA

02-05 How hedge funds use the CA

作者: 非常暴龙兽 | 来源:发表于2019-06-13 14:10 被阅读0次

Two stock scenario:

A: predict +1% over mkt, long $50, \beta_A=1.0
B: predict -1% below mkt, short $50, \beta_B=2.0
then
\gamma_p =\gamma_A + \gamma_B = \beta_A \gamma_M + \alpha_A+\beta_B\gamma_M+\alpha_B

\gamma_M=0大盘没涨也没跌
\gamma_P=\alpha_A+\alpha_B=0.5+0.5= 1 dollar
Two stock CAPM math:
\gamma_P = \sum_i \omega_i(\beta_i \gamma_M+\alpha_i)
=(\omega_A \beta_A +\omega_B \beta_B)\gamma_M+\omega_A \alpha_A +\omega_B\alpha_B
\beta_P=0则纯\alpha套利。

How to allocate A and B?

\beta_A=1.0,\ \ \ \ \alpha_A=+1\%
\beta_A=2.0,\ \ \ \ \alpha_A=-2\%
Find \omega_A and \omega_B so that mkt risk is minimized.
\beta_P=\omega_A \cdot 1 + \omega_B \cdot 2=0
\mathrm{abs}(\omega_A)+\mathrm{abs}(\omega_B)=1
联立方程解出
\omega_A=2/3,\ \ \ \ \omega_B=-1/3
CAPM for hedge funds summary
Assuming:

  • Information >> \alpha_i
  • \beta_i

CAPM enables:

  • minimize mkt risk, \beta_P=0
  • \omega_i, long-short

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