Samuel Clark Department of Sociology, University of Washington Institute of Behavioral Science, University of Colorado at Boulder Agincourt Health and Population Unit, University of the Witwatersrand Using & Interpreting the Single Decrement Life Table Examples
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Using & Interpreting the Single Decrement Life Table
Using & Interpreting the Single Decrement Life Table. Examples. Plan. Review Period Life Table Construction Ways of using the life table The life table as a Stationary Population Examples Life tables from South Africa Life tables from Zambia Life tables from the USA. - PowerPoint PPT Presentation
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Samuel Clark
Department of Sociology, University of WashingtonInstitute of Behavioral Science, University of Colorado at Boulder
Agincourt Health and Population Unit, University of the Witwatersrand
Using & Interpreting the Single Decrement Life Table
Examples
2
Plan
Review Period Life Table Construction Ways of using the life table The life table as a Stationary Population Examples
– Life tables from South Africa– Life tables from Zambia– Life tables from the USA
3
Creating a Period Life Table
The data available are usually observed age-specific mortality rates, nMx
Critical assumption is that nMx~ nmx
The trick then is to convert these observed age-specific mortality rates into one of the columns of a life table
The most convenient choice is to convert to nqx
nMx to nqx conversion:
1
n xn x
n x n x
n mq
n a m
4
Strategies for Choosing nax
nmx nqx requires nax … where do we get nax ?
From calculating it directly From smoothing (graduating) the death distribution within
each age interval Borrowing values from another population Making one of two assumptions:
– nax is half the length of the age interval (n/2), or
– nmx is constant in the interval which negates the necessity of using nax because there is a direct formula to calculate
npx: n xn mn xp e
5
nax in Practice
Usually use n/2 for all age groups except the first Mortality rate between ages 0 and 5 changes very
rapidly, falling very quickly at first and then flattening out Consequently most deaths early in life occur closer to 0
than to 5 and hence nax is significantly less than n/2 in the first two age groups (0, 1-4)
In general in other age groups where mortality is changing less rapidly, the overall life table is very insensitive to the exact choice of nax
6
nax for Very Young Ages
Males Females
Value of 1a0
I f 1m0 >= 0.107 0.330 0.350I f 1m0 < 0.107 0.045+2.684(1m0) 0.053+2.800(1m0)
Value of 4a1
I f 1m0 >= 0.107 1.352 1.361I f 1m0 < 0.107 1.651-2.816(1m0) 1.522-1.518(1m0)
In constructing a period life table, we usually start by assuming that the observed mortality rates are equal to the life table mortality rates: nmx ~nMx
n xn x
n x
dm
L
9
Life Table Columns: nax
Average number of years lived in the age interval by those dying in the age interval
We must acquire the nax values from somewhere, discussed previously
n xa
10
Life Table Columns: nqx
n xn x
x
dq
l
Probability of dying between ages x and x+n
This is where we usually start constructing the life table:
1
n xn x
n x n x
n Mq
n a M
11
Life Table Columns: npx
Probability of surviving from ages x to x+n
1x n x n xn x n x
x x
l l dp q
l l
12
Life Table Columns: lx
x n x n xl l p Survivors, number left alive at age x+n
13
Life Table Columns: ndx
Number dying between ages x and x+n
n x x x nd l l
14
Life Table Columns: nLx
Person-years lived between ages x and x+n
Because n is effectively infinite for the open (last) age interval, we cannot calculate nLx given the formulas we have:
n x x n n x n xL n l a d
xx
x
lL
m
15
Life Table Columns: Tx
Person-years lived at ages older than x
x n aa x
T L
16
Life Table Columns: ex
Expectation of life at age x; average additional years of life that someone who survives to age x can expect to live
Single-Life-Table-Template.xls
0 xx
x
Te
l
17
Additional Ways of Using a Life Table
Probability of surviving from age x to age y
Probability of dying between ages x and y
Number of people dying between ages x and y
Number of person years lived between ages x and y
Probability that a newborn will die between ages x and x+n
yy x x
x
lp
l
x y y x xl l d
1 1 y x y y x x
y x x y x xx x x
l l l dq p
l l l
x y y x xT T L
0
n xdl
18
Additional Ways of Using a Life Table
Probability that a newborn will experience their death between ages x and y
Number of years that a newborn can expect to live between ages x and y
Probability that newborn will survive to age x
Probability that a newborn will die before age x
0
( ) xlp xl
0 0
0 0 0
( ) 1 ( ) 1 x xx l l dlq x p x
l l l
0 0
x y y x xl l d
l l
0
x yT T
l
19
The Life Table as Stationary Population
A stationary population has:– Age-specific mortality constant through time– The number of births constant through time– Net migration = 0 at all ages
size and age structure that are constant through time