September 2013 - Q1(iii)

Discussion in 'SA4' started by Páudi Hegarty, Sep 4, 2023.

  1. Hi there,

    This Q is also in the tutorial 2 slides and tutorial 2 Qs.

    Mark scheme for roll forward:

    Pensioners – £100m x 1.04 - (£5m x 1.04^0.5 x 1.029^0.5)= £98.8m

    Why doesn't the £100m get pension increases, aka 100m x 1.029 x 1.04 - (£5m x 1.04^0.5 x 1.029^0.5)

    Similarly, why does the roll forward for actives not apply one year of salary increases (£70m x 1.055 x 1.04) as opposed to just £70m x 1.055?
     
  2. Gresham Arnold

    Gresham Arnold ActEd Tutor Staff Member

    Hi

    In summary, when we roll forward accrued liabilities, the pension increases or salary increases are already in the liability figure, so we just need to multiply by (1+i). Consultancies that I worked for called this 'unwinding the discount rate'.

    More formally, we can demonstrate this by valuing a deferred pension at the beginning of the year (BOY) and end of the year (EOY) and then comparing the values. Let:
    - DP be the amount of the deferred pension (£ pa) at a particular point in time
    - other nomenclature be as per the SP4 / SA4 courses

    Value of DP@BOY = DP@BOY x [(1+r)/(1+i)]^(NRA-x) x annuity

    Value of DP@EOY = DP@EOY x [(1+r)/(1+i)]^(NRA-(x+1)) x annuity
    (since at the end of the year, the member will be a year older)

    Assume that DP@EOY = DP@BOY x (1+r)
    (in other words, actual DP revaluation that year was as assumed)

    Therefore: Value of DP@EOY:
    = DP@BOY x (1+r) x[(1+r)/(1+i)]^(NRA-x-1) x annuity
    = DP@BOY x (1+r)^(NRA-x) / [(1+i)^(NRA-x-1)] x annuity

    So, Value of DP@EOY / Value of DP@BOY = (1+i)

    Therefore Value of DP@EOY = Value of DP@BOY x (1+i)

    Hope that helps!
    Gresham
     
  3. Perfect, thanks Gresham!
     

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