214 BUREAU OF AMERICAN ETHNOLOGY [Bull. 197 



In appendix table 2, only the Z™ values are given (i.e., the number 

 of survivors within the specified age groups for males only). The 

 values for females must, of course, be obtained separately. 



Stey 5. A set of derived survivorsliip values (Z'™ values) are then 

 calculated by multiplying the Z^ values by the corresponding e-"' 

 values. The identical procedure is followed in obtaining L'^ values 

 from the Z^ values given in the same model. 



Step 6. In order to facilitate comparisons among age distributions, 

 the Z'" and Z^ values may be expressed as percentages of the combined 

 total of these values, for both sexes. 



Stej) 7. An approximation of the value of Zo and 3Z1 (for each 

 sex separately) can then be obtained by applying the following for- 

 mulas to the li and I5 values (expressing the number of survivors to 

 exact age 1 and 5, respectively) for each sex, as provided in the basic 

 United Nations source.^ The formulas are as follows : 



Zo=25,000 plus (0.75) (li) (for each sex separately). In appendix 

 table 2, the 1 "* value for the specified model life table is given as 

 91,553. 



3Zi= (1.9) (li) plus (2.1) (I5) (for each sex separately). In appen- 

 dix table 2 the 1™ value for the specified model life table is given as 

 88,513. 



Finally, as a check on the calculations, the approximate value of 

 4Z0 (for each sex separately) can be obtained by the formula: 



4Zo=25,000 plus (2.65) (la) plus (2.1) (I5). It should be noted that 

 the derived Lo' and 3Z/ values are only approximate, but they do yield 

 a percentage distribution for the population under 1 year and 1 to 4 

 years, for each sex, that is sufficiently accurate for most purposes. 



" United Nations, 1956, table III, pp. 76-77. 



