31
 ACTS 4301 FORMULA SUMMARY Lesso n 1: Probabi lit y Review 1. V ar(X)= E[X 2 ]-  E[X ] 2 2.  V ar(aX  + bY ) = a 2 V ar(X ) + 2abCov(X, Y ) + b 2 V ar(Y ) 3.  V ar(  ¯ X ) =  V ar(X ) n 4.  E X [X ] = E Y  [E X [X |Y ]] Double expectation 5.  V ar X [X ] = E Y  [V ar X [X |Y ]] + V ar Y  (E X [X |Y ]) Conditional variance Distribution, Density and Moments for Common Random Variables Continuous Distributions Name  f (x)  F (x)  E[X] Var(X) Exponential  e x θ /θ  1 e x θ  θ θ 2 Uniform  1 ba , x ∈  [ a, b]  x θ , x ∈  [ a, b]  a+b 2 (ba) 2 12 Gamma  x α1 e x θ /Γ(α)θ α   x 0  f (t)dt αθ αθ 2 Discrete Distributions Name  f (x)  E[X] Var(X ) Poisson  e λ λ x /x!  λ λ Binomial m x  p x (1  p) mx mp mp(1  p)

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  • ACTS 4301

    FORMULA SUMMARY

    Lesson 1: Probability Review

    1. Var(X)= E[X2]- E[X]2

    2. V ar(aX + bY ) = a2V ar(X) + 2abCov(X,Y ) + b2V ar(Y )

    3. V ar(X) = V ar(X)n

    4. EX [X] = EY [EX [X|Y ]] Double expectation5. V arX [X] = EY [V arX [X|Y ]] + V arY (EX [X|Y ]) Conditional varianceDistribution, Density and Moments for Common Random Variables

    Continuous Distributions

    Name f(x) F (x) E[X] Var(X)

    Exponential ex / 1 ex 2

    Uniform 1ba , x [a, b] x , x [a, b] a+b2 (ba)2

    12

    Gamma x1ex /()

    x0 f(t)dt

    2

    Discrete Distributions

    Name f(x) E[X] Var(X)

    Poisson ex/x!

    Binomial(mx

    )px(1 p)mx mp mp(1 p)

  • 2Lesson 2: Survival Distributions: Probability Functions, Life Tables

    1. Actuarial Probability Functions

    tpx - probability that (x) survives t years

    tqx - probability that (x) dies within t years

    t|uqx - probability that (x) survives t years and then dies in the next u years.

    t+upx = tpx u px+tt|uqx = tpx u qx+t =

    = tpx t+u px == t+uqx t qx

    2. Life Table Functions

    dx = lx lx+1ndx = lx lx+nqx = 1 px = dx

    lx

    tpx =lx+tlx

    t|uqx =lx+t lx+t+u

    lx3. Mathematical Probability Functions

    tpx = ST (x)(t)

    tqx = FT (x)(t)

    t|uqx = Pr (t < T (x) t+ u) = FT (x)(t+ u) FT (x)(t) =

    = Pr (x+ t < X x+ t+ u|X > x) = FX(x+ t+ u) FX(x+ t)sX(x)

    Sx+u(t) =Sx(t+ u)

    Sx(u)

    Sx(t) =S0(x+ t)

    S0(x)

    Fx(t) =F0(x+ t) F0(x)

    1 F0(x)

  • 3Lesson 3: Survival Distributions: Force of Mortality

    x =f0(x)

    S0(x)= d

    dxlnS0(x)

    x+t =fx(t)

    Sx(t)= d

    dxlnSx(t)

    Sx(t) =t px = exp

    ( t

    0x+sds

    )= exp

    ( t

    0x(s)ds

    )= exp

    ( x+tx

    sds

    )x(t) = dtpx/dt

    tpx= d lnt px

    dt

    fT (x)(t) = fx(t) =t px x(t)

    t|uqx = t+ut

    spx x(s)ds

    tqx =

    t0spx x(s)ds

    If x(t) = x(t) + k for all t, then sp

    x = spxe

    kt

    If x(t) = x(t) + x(t) for all t, then spx = spxspx

    If x(t) = kx(t) for all t, then sp

    x = (spx)

    k

  • 4Lesson 4: Survival Distributions: Mortality Laws

    Constant Force of Mortality

    x(t) =

    tpx = et

    Uniform distribution (De Moivres law)

    x(t) =1

    x t , 0 t x

    tpx = x t x , 0 t x

    tqx =t

    x, 0 t x

    t|uqx =u

    x, 0 t+ u xBeta distribution (Generalized De Moivres law)

    x(t) =

    x ttpx =

    ( x t x

    ), 0 t x

    Gompertzs law:

    x = Bcx, c > 1

    tpx = exp

    (Bc

    x(ct 1)ln c

    )Makehams law:

    x = A+Bcx, c > 1

    tpx = exp

    (At Bc

    x(ct 1)ln c

    )Weibull Distribution

    x = kxn

    S0(x) = ekxn+1/(n+1)

  • 5Lesson 5: Survival Distributions: Moments

    Complete Future Lifetime

    ex =

    0

    ttpxx+tdt

    ex =

    0

    tpxdt

    ex =1

    for constant force of mortality

    ex = x

    2for uniform (de Moivre) distribution

    ex = x+ 1

    for generalized uniform (de Moivre) distribution

    E[(T (x))2

    ]= 2

    0

    ttpxdt

    V ar (T (x)) =1

    2for constant force of mortality

    V ar (T (x)) =( x)2

    12for uniform (de Moivre) distribution

    V ar (T (x)) =( x)2

    (+ 1)2(+ 2)for generalized uniform (de Moivre) distribution

    n-year Temporary Complete Future Lifetime

    ex:n =

    n0ttpxx+tdt+ nnpx

    ex:n =

    n0

    tpxdt

    ex:n =n px(n) +n qx(n/2) for uniform (de Moivre) distribution

    ex:1 = px + 0.5qx for uniform (de Moivre) distribution

    ex:n =1 en

    for constant force of mortality

    E[(T (x) n)2

    ]= 2

    n0ttpxdt

    Curtate Future Lifetime

    ex =

    k=1

    kk|qx

    ex =

    k=1

    kpx

    ex = ex 0.5 for uniform (de Moivre) distribution

    E[(K(x))2

    ]=k=1

    (2k 1)kpx

    V ar (K(x)) = V ar (T (x)) 112

    for uniform (de Moivre) distribution

  • 6n-year Temporary Curtate Future Lifetime

    ex:n =n1k=1

    kk|qx + nnpx

    ex:n =nk=1

    kpx

    ex:n = ex:n 0.5nqx for uniform (de Moivre) distribution

    E[(K(x) n)2

    ]=

    nk=1

    (2k 1)kpx

  • 7Lesson 6: Survival Distributions: Percentiles, Recursions, and Life Table Concepts

    Recursive formulas

    ex = ex:n +n pxex+n

    ex:n = ex:m +m pxex+m:nm, m < nex = ex:n +n pxex+n = ex:n1 +n px(1 + ex+n)

    ex = px + pxex+1 = px(1 + ex+1)

    ex:n = ex:m +m pxex+m:nm == ex:m1 +m px(1 + ex+m:nm) m < n

    ex:n = px + pxex+1:n1 = px(

    1 + ex+1:n1)

    Life Table Concepts

    Tx =

    0

    lx+tdt, total future lifetime of a cohort of lx individuals

    nLx =

    n0lx+tdt, total future lifetime of a cohort of lx individuals over the next n years

    Yx =

    0

    Tx+tdt

    ex =Txlx

    ex:n =nLxlx

    Central death rate and related concepts

    nmx =ndx

    nLx

    mx =qx

    1 0.5qx for uniform (de Moivre) distributionnmx = x for constant force of mortality

    a(x) =Lx lx+1

    dxthe fraction of the year lived by those dying during the year

    a(x) =1

    2for uniform (de Moivre) distribution

  • 8Lesson 7: Survival Distributions: Fractional Ages

    Function Uniform Distribution of Deaths Constant Force of Mortality Hyperbolic Assumption

    lx+s lx sdx lxpsx lx+1/(px + sqx)sqx sqx 1 psx sqx/(1 (1 s)qx)spx 1 sqx psx px/(1 (1 s)qx)sqx+t sqx/(1 tqx), 0 s+ t 1 1 psx sqx/(1 (1 s t)qx)x+s qx/(1 sqx) ln px qx/(1 (1 s)qx)

    spxx+s qx psx(ln px) pxqx/(1 (1 s)qx)2mx qx/(1 0.5qx) ln px q2x/(px ln px)Lx lx 0.5dx dx/ ln px lx+1 ln px/qxex ex + 0.5

    ex:n ex:n + 0.5nqx

    ex:1 px + 0.5qx

  • 9Lesson 8: Survival Distributions: Select Mortality

    When mortality depends on the initial age as well as duration, it is known as select mortality,since the person is selected at that age. Suppose qx is a non-select or aggregate mortality andq[x]+t, t = 0, , n 1 is select mortality with selection period n. Then for all t n, q[x]+t = qx+t.

  • 10

    Lesson 9: Insurance: Payable at Moment of Death - Moments - Part 1

    Ax =

    0

    ettpxx(t) dt

    Actuarial notation for standard types of insurance

    Name Present value random variable Symbol for actuarial present value

    Whole life insurance vT Ax

    Term life insurancevT T n0 T > n

    A1x:n

    Deferred life insurance0 T nvT T > n n

    |Ax

    Deferred term insurance0 T nvT n < T n+m0 T > n

    n|A1x:m =n |mAx

    Pure endowment0 T nvn T > n

    A 1x:n or nEx

    Endowment insurancevT T nvn T > n

    Ax:n

  • 11

    Lesson 10: Insurance: Payable at Moment of Death - Moments - Part 2

    Actuarial present value under constant force and uniform (de Moivre) mortality for insurances payableat the moment of death

    Type of insurance APV under constant force APV under uniform (de Moivre)

    Whole life +axx

    n-year term +(1 en(+)) anx

    n-year deferred life +en(+)

    ena(x+n)x

    n-year pure endowment en(+) en((x+n))

    x

    j-th moment Multiply by j

    in each of the above formulae

    Gamma Integrands 0

    tnet dt =n!

    n+1 u0tet dt =

    1

    2

    (1 (1 + u)eu

    )=au uvu

    Variance

    If Z3 = Z1 + Z2 and Z1, Z2 are mutually exclusive, then

    V ar(Z3) = V ar(Z1) + V ar(Z2) 2E[Z1]E[Z2]

  • 12

    Lesson 11: Insurance: Annual and m-thly: Moments

    Ax =0

    k|qxvk+1 =0

    kpxqx+kvk+1

    Actuarial present value under constant force and uniform (de Moivre) mortality for insurances payableat the end of the year of death

    Type of insurance APV under constant force APV under uniform (de Moivre)

    Whole life qq+iaxx

    n-year term qq+i (1 (vp)n)anx

    n-year deferred life qq+i(vp)n

    vna(x+n)x

    n-year pure endowment (vp)n vn((x+n))

    x

  • 13

    Lesson 12: Insurance: Probabilities and Percentiles

    Summary of Probability and Percentile Concepts

    To calculate Pr(Z z) for continuous Z, draw a graph of Z as a function of T . Identifyparts of the graph that are below the horizontal line Z = z, and the corresponding ts. Thencalculate the probability of T being in the range of those ts.

    Note that

    Pr(Z < z) = Pr(vt < z) = Pr(t > ln z

    )=t px, where t

    = ln z

    = ln z

    ln(1 + i)

    The following table shows the relationship between the type of insurance coverage and corre-sponding probability:

    Type of insurance Pr(Z < z)

    Whole life tpx

    n-year term

    {npx z

    vntpx z

    > vn

    n-year deferred life

    {nqx +t px z

    < vn1 z vn

    n-year endowment

    {0 z < vn

    tpx z vn

    n-year deferred m-year term

    nqx +n+m px z < vm+n

    nqx +t px vm+n z < vn

    1 z vn

    In the case of constant force of mortality and interest , Pr(Z z) = z/ For discrete Z, identify T and then identify K + 1 corresponding to those T . In other words,Pr(Z > z) = Pr (T < t) =k qx, where k = btc - the greatest integer smaller than tPr(Z < z) = Pr (T > t) =k+1 px, where k = btc - the greatest integer smaller or equal to t To calculate percentiles of continuous Z, draw a graph of Z as a function of T . Identify where

    the lower parts of the graph are, and how they vary as a function of T.For example, for whole life, higher T lead to lower Z.For n-year deferred whole life, both T < n and higher T lead to lower Z.Write an equation for the probability Z less than z in terms of mortality probabilities

    expressed in terms of t. Set it equal to the desired percentile, and solve for t or for ekt for anyk. Then solve for z (which is often vt)

  • 14

    Lesson 13: Insurance: Recursive Formulas, Varying Insurances

    Recursive Formulas

    Ax = vqx + vpxAx+1

    Ax = vqx + v2pxqx+1 + v

    22pxAx+2

    Ax:n = vqx + vpxAx+1:n1A1x:n = vqx + vpxA

    1x+1:n1

    n|Ax = vpxn1|Ax+1A 1x:n = vpxA

    1x+1:n1

    Increasing and Decreasing Insurance 0

    tnetdt =n

    n+1 u0tetdt =

    1

    2

    (1 (1 + u) eu

    )=an uvu

    (IA)x

    =

    (+ )2for constant force

    E[Z2] =2

    (+ 2)3for Z a continuously increasing continuous insurance, constant force.(

    IA)1x:n

    +(DA

    )1x:n

    = nA1x:n(IA)1x:n

    +(DA

    )1x:n

    = (n+ 1)A1x:n

    (IA)1x:n + (DA)1x:n = (n+ 1)A

    1x:n

    Recursive Formulas for Increasing and Decreasing Insurance

    (IA)1x:n = A1x:n + vpx (IA)

    1x+1:n1

    (IA)1x:n = A1x:n + vpx (IAA)

    1x+1:n1

    (DA)1x:n = nA1x:n + vpx (DA)

    1x+1:n1

    (DA)1x:n = A1x:n + (DA)

    1x:n1

  • 15

    Lesson 14: Relationships between Insurance Payable at Moment of Death and Payableat End of Year

    Summary of formulas relating insurances payable at moment of death to insurances payable at theend of the year of death assuming uniform distribution of deaths

    Ax =i

    Ax

    A1x:n =i

    A1x:n

    n|Ax = in|Ax(

    IA)1x:n

    =i

    (IA)1x:n(

    ID)1x:n

    =i

    (ID)1x:n

    Ax:n =i

    A1x:n +A

    1x:n

    A(m)x =i

    i(m)Ax

    2Ax =2i+ i2

    22Ax(

    IA)1x:n

    =(IA)1x:n A1x:n

    (1

    d 1

    )Summary of formulas relating insurances payable at moment of death to insurances payable at theend of the year of death using claims acceleration approach

    Ax = (1 + i)0.5Ax

    A1x:n = (1 + i)0.5A1x:n

    n|Ax = (1 + i)0.5n|AxAx:n = (1 + i)

    0.5A1x:n +A1

    x:n

    A(m)x = (1 + i)(m1)/2mAx

    2Ax = (1 + i)2Ax

  • 16

    Lesson 15: Annuities: Continuous, Expectation

    Actuarial notation for standard types of annuity

    Name Payment per Present value Symbol for actuarialannum at time t random variable present value

    Whole life 1 t T aT axannuity

    Temporary life1 t min(T, n)0 t > min(T, n)

    aT T nan T > n

    ax:n

    annuity

    Deferred life annuity0 t n or t > T1 n < t T

    0 T naT an T > n n|ax

    Deferred temporary0 t n or t > T1 n < t n+m and t T0 T > n+m

    0 T naT an n < T n+man+m an T > n+m

    n|ax:m

    life annuity

    Certain-and-life1 t max(T, n)0 t > max(T, n)

    an T naT T > n

    ax:n

    Relationships between insurances and annuities

    ax =1 Ax

    Ax = 1 axax:n =

    1 Ax:n

    Ax:n = 1 ax:n

    n|ax = Ax:n Ax

    General formulas for expected value

    ax =

    0

    antpxx+t dt

    ax =

    0

    vttpx dt

    ax:n =

    n0vttpx dt

    n|ax = n

    vttpx dt

    Formulas under constant force of mortality

  • 17

    ax =1

    +

    ax:n =1 e(+)n

    +

    n|ax = e(+)n

    +

    Relationships between annuities

    ax = ax:n +n Exax+n

    ax:n = an +n |ax

  • 18

    Lesson 16: Annuities: Discrete, Expectation

    Relationships between insurances and annuities

    ax =1Axd

    Ax = 1 daxax:n =

    1Ax:nd

    Ax:n = 1 dax:nA1x:n = va

    1x:n a1x:n

    (1 + i)Ax + iax = 1

    Relationships between annuities

    ax:n = an +n |axax:n = ax n Exax+nn|ax =n Exax+nax = ax:n +n |axax = ax 1ax:n = ax:n + 1n Ex = ax:n1 + 1

    Other annuity equations

    ax:n =n1k=1

    akk1pxqx+k1 + ann1px

    ax:n =n1k=0

    vkkpx, ax:n =nk=1

    vkkpx

    ax =1 + i

    q + i, if qx is constant

    Accumulated value

    sx:n =ax:n

    nExsx:n = sx+1:n1 + 1

    sx:n = sx+1:n1 +1

    n1Ex+1

    sx:n = sx:n + 1 1nEx

    mthly annuities

    a(m)x =

    k=0

    1

    mvkmkm

    px

  • 19

    Lesson 17: Annuities: Variance

    General formulas for second moments

    E[Y 2x ] =

    0

    a2t tpxx+t dt

    E[Y 2x ] =

    k=1

    a2kk1|qx

    E[Y 2x:n] =nk=1

    a2kk1|qx + npxa2n =

    n1k=1

    a2kk1|qx + n1pxa2n

    Special formulas for variance of whole life annuities and temporary life annuities

    V ar(Yx) =2Ax (Ax)2

    2=

    2(ax 2 ax)

    (ax)2

    V ar(Yx:n) =2Ax:n (Ax:n)2

    2=

    2(ax:n 2 ax:n)

    (ax:n)2

    V ar(Yx) = V ar(Yx) =2Ax (Ax)2

    d2=

    2(ax 2 ax)d2

    +2 ax (ax)2

    V ar(Yx:n) = V ar(Yx:n1) =2Ax:n (Ax:n)2

    d2

  • 20

    Lesson 18: Annuities: Probabilities and Percentiles

    To calculate a probability for an annuity, calculate the t for which at has the desired property.Then calculate the probability t is in that range. To calculate a percentile of an annuity, calculate the percentile of T , then calculate aT . Some adjustments may be needed for discrete annuities or non-whole-life annuities If forces of mortality and interest are constant, then the probability that the present value of

    payments on a continuous whole life annuity will be greater than its actuarial present value is

    Pr(aT (x) > ax) =

    (

    +

    )/

  • 21

    Lesson 19: Annuities: Varying Annuities, Recursive Calculations

    Increasing/Decreasing Annuities(I a)x

    =1

    (+ )2, if is constant(

    I a)x:n

    +(Da)x:n

    = nax:n

    (Ia)x:n + (Da)x:n = (n+ 1)ax:n

    Recursive Formulas

    ax = vpxax+1 + 1

    ax = vpxax+1 + vpx

    ax = vpxax+1 + ax:1ax:n = vpxax+1:n1 + 1ax:n = vpxax+1:n1 + vpxax:n = vpxax+1:n1 + ax:1n|ax = vpxn1ax+1n|ax = vpxn1ax+1n|ax = vpxn1ax+1ax:n = 1 + vqxan1 + vpxax+1:n1ax:n = v + vqxan1 + vpxax+1:n1ax:n = a1 + vqxan1 + vpxax+1:n1

  • 22

    Lesson 20: Annuities: m-thly Payments

    In general:

    a(m)x = a(m)x

    1

    m

    1 + i =

    (1 +

    i(m)

    m

    )m=

    (1 d

    (m)

    m

    )mi(m) = m

    ((1 + i)

    1m 1

    )d(m) = m

    (1 (1 + i) 1m

    )

    For small interest rates:

    a(m)x ax m 1

    2m

    a(m)x ax +m 1

    2m

    Under the uniform distribution of death (UDD) assumption:

    a(m)x = ax m 1

    2m

    a(m)x = ax +m 1

    2m

    a(m)x = (m)ax (m)a

    (m)x:n = (m)ax:n (m)(1n Ex)

    n|a(m)x = (m)n|ax (m)nExax = ()ax ()a

    (m)x:n = a

    (m)x:n

    1

    m+

    1

    mnEx

    a(m)x =1A(m)xd(m)

    Similar conversion formulae for converting the modal insurances to annuities hold for other types ofinsurances and annuities (only whole life version is shown).

    (m) =id

    i(m)d(m)

    (m) =i i(m)i(m)d(m)

    i() = d() = ln(1 + i) =

  • 23

    Woolhouses formula for approximating a(m)x :

    a(m)x ax m 1

    2m m

    2 112m2

    (x + )

    ax ax 12 1

    12(x + )

    a(m)x:n ax:n

    m 12m

    (1n Ex) m2 1

    12m2(x + n Ex(x+n + ))

    n|a(m)x n |ax m 1

    2mnEx m

    2 112m2

    nEx(x+n + )

    ex = ex +1

    2 1

    12x

    When the exact value of x is not available, use the following approximation:

    x 12

    (ln px1 + ln px)

  • 24

    Lesson 21: Premiums: Fully Continuous Expectation

    The equivalence principle: The actuarial present value of the benefit premiums is equal to theactuarial present value of the benefits. For instance:

    whole life insurance Ax = P(Ax)ax

    n year endowment insurance Ax:n = P(Ax:n

    )ax:n

    n year term insurance A 1x:n = P(A 1x:n

    )ax:n

    n year deferred insurance n|Ax =n P(n|Ax

    )ax:n

    n pay whole life insurance Ax =n P(Ax)ax:n

    n year deferred annuity n|ax = P (n|ax) ax:n

    P(Ax)

    =1 axax

    =1

    ax

    P(Ax)

    =Ax

    (1 Ax)/ =Ax

    1 AxP(Ax:n

    )=

    1

    ax:n

    P(Ax:n

    )=

    Ax:n1 Ax:n

    For constant force of mortality, P(Ax)

    and P(Ax:n

    )are equal to .

    Future loss formulas for whole life with face amount b and premium amount pi:

    0L = bvT piaT = bvT pi

    (1 vT

    )= vT

    (b+

    pi

    ) pi

    E[0L] = bAx piax = Ax(b+

    pi

    ) pi

    Similar formulas are available for endowment insurance.

  • 25

    Lesson 22: Premiums: Net Premiums for Discrete Insurances Calculated from LifeTables

    Assume the following notation

    (1) Px is the premium for a fully discrete whole life insurance, or Ax/ax(2) P 1x:n is the premium for a fully discrete n-year term insurance, or A

    1x:n/ax:n

    (3) P 1x:n is the premium for a fully discrete n-year pure endowment, or A1

    x:n/ax:n(4) Px:n is the premium for a fully discrete n-year endowment insurance, or Ax:n/ax:n

  • 26

    Lesson 23: Premiums: Net Premiums for Discrete Insurances Calculated fromFormulas

    Whole life and endowment insurance benefit premiums

    Px =1

    ax d

    Px =dAx

    1AxPx:n =

    1

    ax:n d

    Px:n =dAx:n

    1Ax:nFor fully discrete whole life and term insurances:If qx is constant, then Px = vqx and P

    1x:n = vqx.

    Future loss at issue formulas for fully discrete whole life with face amount b:

    L0 = vKx+1

    (b+

    Pxd

    ) Px

    d

    E[L0] = Ax

    (b+

    Pxd

    ) Px

    d

    Similar formulas are available for endowment insurances.

    Refund of premium with interestTo calculate the benefit premium when premiums are refunded with interest during the deferralperiod, equate the premiums and the benefits at the end of the deferral period. Past premiums areaccumulated at interest only.

    Three premium principle formulae

    nPx P 1x:n = P 1x:nAx+nPx:n n Px = P 1x:n(1Ax+n)

  • 27

    Lesson 24: Premiums: Net Premiums Paid on an m-thly Basis

    If premiums are payable mthly, then calculating the annual benefit premium requires dividing by anmthly annuity. If you are working with a life table having annual information only, mthly annuitiescan be estimated either by assuming UDD between integral ages or by using Woolhouses formula(Lesson 20). The mthly premium is then a multiple of the annual premium. For example, for h-paywhole life payable at the end of the year of death,

    hP(m)x =

    Ax

    a(m)

    x:h

    =hPxax:h

    a(m)

    x:h

  • 28

    Lesson 25: Premiums: Gross Premiums

    The gross future loss at issue Lg0 is the random variable equal to the present value at issue of benefitsplus expenses minus the present value at issue of gross premiums:

    Lg0 = PV (Ben) + PV (Exp) PV (P g)To calculate the gross premium P g by the equivalence principle, equate P g times the annuity-due forthe premium payment period with the sum of

    1. An insurance for the face amount plus settlement expenses2. P g times an annuity-due for the premium payment period of renewal percent of premium expense,

    plus the excess of the first year percentage over the renewal percentage3. An annuity-due for the coverage period of the renewal per-policy and per-100 expenses, plus the

    excess of first year over renewal expenses

  • 29

    Lesson 26: Premiums: Variance of Loss at Issue, Continuous

    The following equations are for whole life and endowment insurance of 1. For whole life, drop n.

    V ar(L0) =(

    2Ax:n (Ax:n

    )2)(1 +

    P

    )2V ar(L0) =

    2Ax:n (Ax:n

    )2(1 Ax:n

    )2 , If equivalence principle premium is usedV ar(L0) =

    + 2, For whole life with equivalence principle and constant force of mortality only

    For whole life and endowment insurance with face amount b:

    V ar(L0) =(

    2Ax (Ax)2)(

    b+P

    )2V ar(L0) =

    (2Ax:n

    (Ax:n

    )2)(b+

    P

    )2If the benefit is b instead of 1, and the premium P is stated per unit, multiply the variances by b2.

    For two whole life or endowment insurances, one with b units and total premium P and the otherwith b units and total premium P , the relative variance of loss at issue of the first to second is((b + P ) / (b + P ))2.

  • 30

    Lesson 27: Premiums: Variance of Loss at Issue, Discrete

    The following equations are for whole life and endowment insurance of 1. For whole life, drop n.

    V ar(0L) =(

    2Ax:n (Ax:n)2)(

    1 +P

    d

    )2If equivalence principle premium is used: V ar(0L) =

    2Ax:n (Ax:n)2(1Ax:n)2

    For whole life with equivalence principle and constant force of mortality only: V ar(0L) =q(1 q)q +2 i

    If the benefit is b instead of 1, and the premium P is stated per unit, multiply the variances by b2.For two whole life or endowment insurances, one with b units and total premium P and the otherwith b units and total premium P , the relative variance of loss at issue of the first to second is((bd+ P ) / (bd+ P ))2.

  • 31

    Lesson 28: Premiums: Probabilities and Percentiles of Loss at Issue

    For level benefit or decreasing benefit insurance, the loss at issue decreases with time for wholelife, endowment, and term insurances. To calculate the probability that the loss at issue isless than something, calculate the probabiitiy that survival time is greater than something. For level benefit or decreasing benefit deferred insurance, the loss at issue decreases during

    the deferral period, then jumps at the end of the deferral period and declines thereafter. To calculate the probability that the loss at issue is greater then a positive number,

    calculate the probability that survival time is less than something minus the probabilitythat survival time is less than the deferral period.

    To calculate the probability that the loss at issue is greater than a negative number,calculate the probability that survival time is less than something that is less than thedeferral period, and add that to the probability that survival time is less than somethingthat is greater then the deferral period minus the probability that survival time is lessthan the deferral period.

    For a deferred annuity with premiums payable during the deferral period, the loss at issuedecreases until the end of the deferral period and increases thereafter. The 100pth percentile premium is the premium for which the loss at issue is positive with

    probability p. For fully continuous whole life, this is the loss that occurs if death occurs atthe 100pth percentile of survival time.