DEMOGRAPHIC METHODSComplete Life Table* for the United States, 1996Exact Age x 1 qx (^) x1dx1Lx Tx ex
0 .00732 100,000 732 99,370 7,611,825 76.1
1 .00054 99,268 53 99,240 7,512,455 75.7
2 .00040 99,215 40 99,193 7,413,215 74.7
3 .00031 99,175 31 99,158 7,314,022 73.7
4 .00026 99,144 26 99,130 7,214,864 72.8
5 .00023 99,118 23 99,106 7,115,734 71.8
6 .00021 99,095 21 99,084 7,016,628 70.8
7 .00020 99,074 19 99,064 6,917,544 69.8
8 .00018 99,055 18 99,046 6,818,480 68.8
9 .00016 99,037 15 99,029 6,719,434 67.8
10 .00014 99,022 14 99,014 6,620,405 66.9
.......
.......
.......
80 .05967 49,276 2,940 47,668 411,547 8.4
81 .06566 46,336 3,043 44,676 363,879 7.9
82 .07250 43,293 3,139 41,586 319,203 7.4
83 .08033 40,154 3,225 38,403 277,617 6.9
84 .08936 36,929 3,300 35,141 239,214 6.5
85 (1.00000) 33,629 33,629 204,073 204,073 6.1
Table 2
NOTE: *This is technically an ‘‘interpolated life table’’ and not a complete life table based on single-year data.
SOURCE: This life table is available on the web at http://www.cdc.gov/nchswww/datawh/statab/unpubd/mortabs/lewk2.htm
describe the experience of an actual birth co-
hort—that is, a group of individuals who are born
within a (narrowly) specified interval of time. If we
wished to portray the mortality history of the birth
cohort of 2000, for example, we would have to wait
until the last individual of that cohort has died, or
beyond the year 2110, before we would be able to
calculate all of the values that comprise the life
table. In such a life table, called a generation or
cohort life table, we can explicitly obtain the proba-
bility of individuals surviving to a given age. As is
intuitively clear, however, a generation life table is
suitable primarily for historical analyses of cohorts
now extinct. Any generation life table that we
could calculate would be very much out of date
and would in no way approximate the present
mortality experience of a population. Thus, we
realize the need for the period life table, which
treats a population at a given point in time as a
synthetic or hypothetical cohort. The major drawback
of the period life table is that it refers to no
particular cohort of individuals. In an era of mor-
tality rates declining at all ages, such a life table will
underestimate true life expectancy for any cohort.
The most fundamental data that underlie the
formation of a period life table are the number of
deaths attributed to each age group in the popula-
tion for a particular calendar year (nDx), where x
refers to the exact age at the beginning of the age
interval and n is the width of that interval, and the
number of individuals living at the midpoint of
that year for each of those same age groups (nPx).
To begin the life table’s construction, we take
the ratio of these two sets of input data—nDx and
nPx—to form a series of age-specific death rates, or
nMx: