Oct 2011 Q8 Part iii

Discussion in 'SP9' started by yellowvonpen, Sep 26, 2016.

  1. yellowvonpen

    yellowvonpen Member

    Very puzzled by the calculation for strategy A in part iii. I did it the following way, and I must be missing something obvious...

    Investing 2M in single bond issue --> 20 units at 100,000 each.
    In 1 year, entire portfolio will be worth either 0 (probability 2%) or 20*105,000 = 2.1M (probability 98%).
    E[X] = (0.02)*0 + (0.98)*2.1M = 2.058M
    Absolute VaR = 2.1M
    Relative VaR = 2.058M - 2.1M = -42,000
    Absolute TVaR = [0*.02+2.1M*.005]/.025 = 420,000
    Relative TVaR = 2.058M - 420,000 = 1,638,000

    Where am I going wrong?

    Likewise, for strategy B I get:
    Absolute VaR = 1.89M (2 defaults)
    Relative VaR = 2.058M - 1.89M = 168,000
    Absolute TVaR = [1.68M*0.0006+1.785M*0.0065+1.89M*(0.025-0.0006-0.0065)]/0.025 = 1,857,660
    Relative TVaR = 2,058,000 - 1,857,660 = 200,340

    The directions and orders of magnitude are consistent with the Examiners' Report but I'm not sure where the numbers are coming from (or if mine are completely wrong).
     
    Last edited by a moderator: Sep 26, 2016
  2. Simon James

    Simon James ActEd Tutor Staff Member

    Have you thought about the significance for the VaR of the "97.5%" stated early in the question?
     
  3. yellowvonpen

    yellowvonpen Member

    Sorry, I'm not following...
     
  4. Simon James

    Simon James ActEd Tutor Staff Member

    Sorry, hint too subtle! In your VaR calculation you have not used the 97.5%. Your calculation is independent of the significance level. For VaR we need to look at what is the maximum loss we would suffer 97.5 times out of 100.

    Now, 98 times out of 100, we get our bond repaid (we don't suffer any losses at all).

    Any help?
     
  5. yellowvonpen

    yellowvonpen Member

    Ah, your last sentence about not suffering any losses at all caused me to realize something: I realized I was doing the VaR/TVaR of the value of the bonds, not the VaR/TVaR of the net loss to the investor. If I simply incorporate the initial cost to the investor ($2M) and then redo the calculations, I get the right answers. Thanks!

    Strategy A VaR: Gain 100,000 98% of the time --> VaR = -100,000
    Strategy A TVaR: [(2M-0)*.02+(2M-2.1M)*.005]/.025 = 1,580,000

    Strategy B VaR: Lose 215,000 or more 0.71% of the time vs. lose 110,000 or more 5.99% of the time --> VaR = 110,000
    Strategy B TVaR: [(2M-1.68M)*0.0006+(2M-1.785M)*0.0065+(2M-1.89M)*(0.025-0.0006-0.0065)]/0.025 = 142,340 (They rounded in the Examiners' Report)
     
    Simon James likes this.

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