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PROCEEDINGS May 15, 16, 17, 18, 2005 - Casualty Actuarial Society

PROCEEDINGS May 15, 16, 17, 18, 2005 - Casualty Actuarial Society

PROCEEDINGS May 15, 16, 17, 18, 2005 - Casualty Actuarial Society

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468 A NEW METHOD OF ESTIMATING LOSS RESERVESwhich leads to the first estimate of the total incurred for accidentyear i given the incurred losses through development year j:Ŝ (1) C iji= P jr=0 E[Y (N+1¡r) ] (12)i.e., the loss development factor from j to ultimate isLDF (1)j,N = 1P jr=0 E[Y (N+1¡r)](13)for j =0,1,:::,N. Alternatively, we may use"#Ŝ (2)1i= C ij E P jr=0 Y (N+1¡r)(14)which yields the alternative loss development factor from j toultimate"#LDF (2)j,N = E 1P jr=0 Y : (<strong>15</strong>)(N+1¡r)From Jensen’s inequality, LDF (2)j,N ¸ LDF(1) j,Nfor every j. Beforecalculating the values of LDF (1)j,Nand LDF(2)j,Nfor various valuesof j and N, the distribution of the Y (j) ’s will be provided.From the theory of the random division of an interval of unitlength (for example, David [6, chapter 5.4] or Feller [9, chapter1]), the variables Y 1 ,Y 2 ,:::,Y N+1 form an exchangeablesequence of dependent random variables with joint pdf:f(y 1 ,y 2 ,:::,y N+1 )8>< (N +1)! if y j ¸ 0 and=>:0 otherwise:N+1 Xk=1y k =1:

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