Tag Archives: demography

Proportion of people alive in 1945 that are still alive

In demography, we like to use life tables to estimate the probability that someone born in 1945 (say) is still alive nowadays.  But another interesting quantity might be the probability that someone alive in 1945 is still alive nowadays.

The main difference is that we do not know when that person, alive in 1945, was born. Someone who was old in 1945 is very unlikely still alive in 2017. To compute those probabilities, we can use datasets from http://www.mortality.org/hmd/. More precisely, we need both death and birth data. I assume that datasets (text files) were downloaded (it is necessary to register – for free – to get the data).

D=read.table("FRDeaths_1x1.txt",skip=1,header=TRUE)
B=read.table("FRBirths.txt",skip=1,header=TRUE)

In the death dataset, there is a “110+” for people older than 110 years. For convenience, let us cap our observations at 110 years old,

D$Age=as.numeric(as.character(D$Age))
D$Age[is.na(D$Age)]=110

Consider now a first function that will return, for people born in 1930 (say) two informations

  • the number of people (here, let us consider women only) born in 1930 (from the birth database)
  • the number of death of people of age 0 in 1930, people of age 1 in 1931, people of age 2 in 1932, etc…

The code is simple

nb=function(y=1930){
debut=1816
MatDFemale=matrix(D$Female,nrow=111)
colnames(MatDFemale)=debut+0:198
cly=y-debut+1:111
deces=diag(MatDFemale[,cly[cly%in%1:199]])
return(c(B$Female[B$Year==y],deces))}

We have a single number for the number of births, and then a vector for the number of deaths. Consider now another function. Consider the people born in 1930. We want to get two numbers : the number of people still alive in 1945 (say), and the number of people still alive nowadays. The ratio will be the proportion of people born in 1930 that were alive in 1945, that are still alive in 2015.

pop=function(ne=1930,an=1945){
comptage=nb(ne)
s=0
if(an>ne) s=sum(comptage[seq(2,1+an-ne)])
p1=max(comptage[1]-s,0)
p2=max(p1-sum(comptage[seq(2+an-ne,length(comptage))]),0)
c(p1,p2)
}

Then, for a given year (say 1945), to get the proportion of people alive in 1945 that are still alive today, we need to count how many people born in 1944 were still alive in 1945, and in 2015, but also born in 1943, 1942, etc, And we simply consider the ratio of the total number of people alive in 2015 over the total number of people alive in 1945

ptn=function(y=1945){
V=Vectorize(function(x) pop(x,y))(1816:y)
sum(V[2,!is.na(V[2,])])/sum(V[1,!is.na(V[1,])])
}

Hence, 22% of those alive in 1945 are still alive in 2015,

> ptn(1945)
[1] 0.2209435

Actually, instead of looking only at 1945, it is possible to get a plot

P=Vectorize(ptn)(1900:2010)
plot(1900:2010,P,type="l",ylim=0:1)

For instance,

> ptn(1975)
[1] 0.6377413

i.e. 63.7% of those alive in 1975 are stil alive 40 years after. That is a rather interesting function, I was surprised that I couldn’t find it is standard demographical R package…

Mortality by Weekday and Age

A few days ago, I did mention on Twitter a nice graph, with

My colleague Jean-Philippe was extremely sceptical, so I tried to reproduce that graph. The good thing is that we have the Social Security Death Master File, for data in the US. To be more specific, I have three big files on my hard drive, and in order to reproduce that graph, we’ll load the data by chunks. But before, because we have the day of birth, and the day of death, I need a function to compute the age. So here it is

> age_years <- function(earlier, later)
+ {
+   lt <- data.frame(earlier, later)
+   age <- as.numeric(format(lt[,2],format="%Y")) - as.numeric(format(lt[,1],format="%Y"))
+   dayOnLaterYear <- ifelse(format(lt[,1],format="%m-%d")!="02-29",
+                            as.Date(paste(format(lt[,2],format="%Y"),"-",format(lt[,1],format="%m-%d"),sep="")),
+                            ifelse(as.numeric(format(later,format="%Y")) %% 400 == 0 | as.numeric(format(later,format="%Y")) %% 100 != 0 & as.numeric(format(later,format="%Y")) %% 4 == 0,
+                                   as.Date(paste(format(lt[,2],format="%Y"),"-",format(lt[,1],format="%m-%d"),sep="")),
+                                   as.Date(paste(format(lt[,2],format="%Y"),"-","02-28",sep=""))))
+   age[which(dayOnLaterYear > lt$later)] <- age[which(dayOnLaterYear > lt$later)] - 1
+   age
+ }

from github.com/nzcoops. Now, it is possible to create a similar table, based on that huge file (we have almost 50 million observations)

> cols <- c(1,9,20,4,15,15,1,2,2,4,2,2,4,2,5,5,7)
> noms_col <- c ("code","ssn","last_name","name_suffix","first_name","middle_name","VorPCode","date_death_m","date_death_d","date_death_y","date_birth_m","date_birth_d","date_birth_y","state","zip_resid","zip_payment","blanks")
> library(LaF)

> TABLE_AGE_DAY=function(temp = "ssdm3"){
+ ssn <- laf_open_fwf( temp,column_widths = cols,column_types=rep("character",length(cols) ),column_names = noms_col,trim = TRUE)
+ object.size(ssn)
+ go_through <- seq(1,nrow(ssn),by = 1e05 )
+ if(go_through[ length(go_through)] != nrow( ssn)) go_through <- c(go_through,nrow( ssn))
+ go_through <- cbind(go_through[-length(go_through)],c(go_through[-c(1,length(go_through)) ]-1,go_through [ length(go_through)]))
+ go_through
+ 
+ pb <- txtProgressBar(min = 0, max = nrow( go_through), style = 3)
+ count_birthday <- function(s){
+   #print(s)
+   setTxtProgressBar(pb, s)
+   data <- ssn[ go_through[s,1]:go_through[s,2],c("date_death_y","date_death_m","date_death_d",
+                                                  "date_birth_y","date_birth_m","date_birth_d")]
+   date1=as.Date(paste(data$date_birth_y,"-",data$date_birth_m,"-",data$date_birth_d,sep=""),"%Y-%m-%d")
+   date2=as.Date(paste(data$date_death_y,"-",data$date_death_m,"-",data$date_death_d,sep=""),"%Y-%m-%d")
+   idx=which(!(is.na(date1)|is.na(date2)))
+   date1=date1[idx]
+   date2=date2[idx]
+   itg=try(age<-age_years(date1,date2),silent=TRUE)
+   if(inherits(itg, "try-error")) age=trunc((date2-date1)/365.25)
+   w=weekdays(date2)
+   T=table(age,w)
+   Tab=matrix(0,106,7)
+   for(i in 1:nrow(T)) if(as.numeric(rownames(T)[i])<106) Tab[as.numeric(rownames(T)[i]),]=T[i,]
+   return(Tab)
+ }
+ D <- lapply( seq_len(nrow( go_through)),count_birthday) 
+ T=D[[1]]
+ for(s in 2:length(D)) T=T+D[[s]]
+ return(T)
+ }

If we run that function on the three files

> D1=TABLE_AGE_DAY("ssdm1")
|========================================| 100%
> D2=TABLE_AGE_DAY("ssdm2")
|========================================| 100%
> D3=TABLE_AGE_DAY("ssdm3")
|========================================| 100%

we can visualize not percentages, as on the figure above, but counts

> D=D1+D2+D3
> colnames(D)=
c("Sun","Thu","Mon","Tue","Wed","Sat","Fri")
> D=D1[,
c("Sun","Mon","Tue","Wed","Thu","Fri","Sat")]

and we have here (I remove the Saturday to get a better output)

> D[,1:6]
          Sun    Mon    Tue    Wed    Thu    Fri
  [1,]   2843   2888   2943   3020   2979   3038
  [2,]   2007   1866   1918   1974   1990   2137
  [3,]   1613   1507   1532   1530   1515   1613
  [4,]   1322   1256   1263   1259   1207   1330
  [5,]   1155   1061   1092   1128   1112   1171
  [6,]   1067    985    950   1082   1009   1055
  [7,]   1129    901    915    954    941   1044
  [8,]   1026    927    944    935    911   1005
  [9,]   1029   1012    871    908    939    998
 [10,]   1093   1011    974    958    928   1018
 [11,]   1106   1031   1019   1036   1087   1122
 [12,]   1289   1219   1176   1215   1141   1292
 [13,]   1618   1455   1487   1484   1466   1633
 [14,]   2121   2000   1900   1941   1845   2138
 [15,]   2949   2647   2519   2499   2524   2748
 [16,]   4488   3885   3798   3828   3747   4267
 [17,]   5709   4612   4520   4422   4443   5005
 [18,]   7280   5618   5400   5271   5344   5986
 [19,]   8086   6172   5833   5820   6004   6628
 [20,]   8389   6507   6166   6055   6430   6955
 [21,]   8794   7038   6794   6628   6841   7572
 [22,]   8578   6528   6512   6472   6757   7342
 [23,]   8345   6750   6483   6469   6714   7338
 [24,]   8361   6859   6589   6623   6854   7369
 [25,]   8398   6974   6892   6766   6964   7613
 [26,]   8432   7210   7012   7175   7343   7801
 [27,]   8757   7641   7526   7352   7674   7950
 [28,]   9190   8041   7843   7851   7940   8268
 [29,]   9495   8409   8555   8400   8469   8934
 [30,]   9876   9041   9015   9166   9106   9641
 [31,]  10567   9952   9506   9634   9770  10212
 [32,]  11417  10428  10402  10275  10455  11169
 [33,]  11992  11306  11124  11095  11243  11749
 [34,]  12665  12327  11760  12025  12137  12443
 [35,]  13629  13135  13179  13037  12968  13724
 [36,]  14560  14009  13927  13822  14105  14436
 [37,]  15660  14990  15013  15009  15101  15700
 [38,]  16749  16504  16148  16091  15912  16863
 [39,]  17815  17760  17519  17144  17553  17943
 [40,]  19366  19057  18918  18517  18760  19604
 [41,]  20770  20458  20154  20339  20349  21238
 [42,]  21962  22194  22020  21499  21690  22347
 [43,]  23803  23922  23701  23681  23437  24227
 [44,]  25685  26133  25559  25209  25287  26115
 [45,]  27506  28110  27363  27042  27272  28228
 [46,]  29366  29744  29555  29245  29678  30444
 [47,]  31444  32193  31817  31504  31753  32302
 [48,]  33452  34719  33529  33954  33441  34618
 [49,]  36186  37150  36005  36064  36226  37138
 [50,]  38401  39244  38813  38465  38506  39884
 [51,]  40331  41830  41168  41110  40937  42014
 [52,]  43181  44351  43975  43949  43579  44734
 [53,]  45307  47134  46522  46149  46089  47286
 [54,]  47996  49441  49139  48678  48629  49903
 [55,]  50635  52424  51757  51433  51477  52550
 [56,]  53509  55337  54556  54482  54406  55906
 [57,]  55703  58482  58016  57400  57097  58758
 [58,]  59016  61453  60652  61024  60557  62473
 [59,]  62475  65651  64169  63824  63829  65592
 [60,]  66621  69185  68885  68217  68752  69963
 [61,]  69759  73144  72421  71784  71745  73414
 [62,]  80346  84253  83044  83177  82416  83833
 [63,]  86851  90059  89002  88985  89245  90334
 [64,]  91839  95465  94602  93985  94154  96195
 [65,]  98461 102846 101348 101328 101306 103170
 [66,] 104569 108722 107768 107711 107729 109350
 [67,] 111230 115477 114418 114743 113935 116356
 [68,] 116999 122053 120727 120342 119782 122926
 [69,] 123695 128339 127184 126822 126639 129037
 [70,] 129956 136123 134555 135120 133842 137390
 [71,] 137984 142964 141316 142855 141419 143620
 [72,] 145132 150708 148407 149345 149448 151910
 [73,] 152877 157993 155861 156349 155924 158725
 [74,] 159109 164652 162722 163499 163157 165744
 [75,] 165848 172121 170730 170482 170585 173431
 [76,] 172457 179036 177185 177328 177392 180215
 [77,] 179936 185015 183223 183932 183237 186663
 [78,] 185900 191053 189986 189730 189639 193038
 [79,] 191498 196694 194246 194810 195246 197812
 [80,] 195505 201289 199684 199561 198968 203226
 [81,] 199031 204927 202204 202622 202951 205792
 [82,] 201589 207928 204929 204001 204396 208224
 [83,] 201665 206743 205194 204676 205256 207980
 [84,] 200965 205653 203422 202393 203422 206012
 [85,] 197445 202692 199498 199730 200075 201728
 [86,] 192324 195961 193589 194754 193800 196102
 [87,] 183732 188063 185153 186104 186021 188176
 [88,] 174258 177474 175822 176078 176761 177449
 [89,] 163180 166706 162810 164367 164281 166436
 [90,] 149169 151738 150148 150212 150535 152435
 [91,] 134218 136866 134959 134922 135027 136381
 [92,] 118936 121106 119591 119509 119793 120998
 [93,] 102734 104955 102944 102865 103345 104776
 [94,]  87418  88885  88023  86963  87546  87872
 [95,]  72023  72698  72151  71579  71530  72287
 [96,]  56985  58238  57478  57319  57163  57615
 [97,]  44447  45058  44607  44469  43888  44868
 [98,]  33457  34132  33022  33409  33454  33642
 [99,]  24070  24317  24305  24089  24020  24383
[100,]  17165  17295  16755  17115  16957  17207
[101,]  11799  12125  11709  11816  11824  11719
[102,]   7714   7741   7959   7691   7648   7633
[103,]   5024   5012   4822   4792   4882   4916
[104,]   2987   3101   2978   3049   3093   2906
[105,]   1781   1894   1811   1756   1734   1834

So clearly, for young people, the number of deaths is rather small…

And to visualize it, as above, we can use

> P=D/apply(D,1,sum)*100
> range(P)
[1] 12.34857 17.59386
> dP=trunc((P-min(P))/(max(P)+.01-min(P))*11)
> library(RColorBrewer)
> CLR=rev(brewer.pal(name="RdYlBu", 11))

> plot(0:1,0:1,ylim=c(55,110),xlim=c(-1,7))
> for(i in 1:106){
+   for(j in 1:7){
+  rect(j-1,108-i,j,107-i,col=CLR[dP[i,j]])
+   }}
> text(rep(-.5,106),107.5-1:106,0:105,cex=.4)

As above, we observe a strong difference among weekdays for the date of death for young people (below 30) which disappear after (even if there is still a sunday effect)

Men set to live as long as women by 2030?

A few months ago, in Men set to live as long as women, figures show, it was mentioned that (in the U.K.)

the gap between male and female life expectancy is closing and men could catch up by 2030, according to an adviser for the Office for National Statistics.

(the slides are available online http://cass.city.ac.uk/…).

Continue reading Men set to live as long as women by 2030?

Your Life in Weeks

This week, I discovered a picture on http://waitbutwhy.com/, which represent a (so-called) typical human life, in weeks,

I found that interesting. But the first problem is that I don’t understand the limit, below: 90 years, that’s not the average life length. That’s not what you should expect to live when you get born. The second problem is that it cannot be as static as it might seem, when you look at the picture. I mean, life expectancy at age 0 is not the same as life expectancy at age 30, or 50. So I did try to make an animated graph, using prospective life tables. Here a code to generate life tables, at different period, for a French population (I distinguish, here male and female)

library(demography)
france.LC1 <- lca(fr.mort,adjust="e0",series="female",years=c(1900,2100))
france.fcast <- forecast(france.LC1,h=100)
L2 <- lifetable(france.fcast)
ex2=L2$ex
L1=lifetable(fr.mort,series="female")
ex1=L1$ex
exF=cbind(ex1,ex2)
france.LC1 <- lca(fr.mort,adjust="e0",series="male",years=c(1900,2100))
france.fcast <- forecast(france.LC1,h=100)
L2 <- lifetable(france.fcast)
ex2=L2$ex
L1=lifetable(fr.mort,series="male")
ex1=L1$ex
exM=cbind(ex1,ex2)
Y=colnames(exF)

Based on those lifetables, we can extract remaining life expectancy, at various ages (say, for instance 50, 51, 52, etc), for someone born on some given year (say 1950). Based on those expected remaining lifetimes, we can plot

picture=function(yearborn=1950,age=50){
k=which(Y==yearborn)
M=diag(exM[,k+0:100])
F=diag(exF[,k+0:100])
par(mfrow=c(1,2))
va=0:(52*100-1)
plot(va%%52,va%/%52,cex=.6,pch=15,col=c("light yellow","light blue","white")[1+
(va>=age*52)*1+(va>(age+M[age+1])*52)*1],ylim=c(100,0),axes=FALSE,xlab="Week",
ylab="Age",main=paste("Man, born on ",yearborn,
", age ",age,sep=""))
axis(1)
axis(2)
plot(va%%52,va%/%52,cex=.6,pch=15,col=c("light yellow","pink","white")[1+
(va>=age*52)*1+(va>(age+F[age+1])*52)*1],ylim=c(100,0),axes=FALSE,xlab="Week",
ylab="Age",main=paste("Woman, born on ",yearborn,
", age ",age,sep=""))
axis(1)
axis(2)}

For instance, if we want the graph above, for someone age 30, born in 1980, we use

picture(1980,30)

Now, if we run a code to get an animated gif, we can get, for someone born in 1950,

and for someone born in 2000

Now, if I could get historical datasets, with the average time spent in schools, ages of retirement, etc, I guess I could add it on the graph. But that’s another story…

Smoothing mortality rates

This morning, I was working with Julie, a student of mine, coming from Rennes, on mortality tables. Actually, we work on genealogical datasets from a small region in Québec, and we can observe a lot of volatiliy. If I borrow one of her graph, we get something like

Since we have some missing data, we wanted to use some Generalized Nonlinear Models. So let us see how to get a smooth estimator of the mortality surface.  We will write some code that we can use on our data later on (the dataset we have has been obtained after signing a lot of official documents, and I guess I cannot upload it here, even partially).

DEATH <- read.table(
"http://freakonometrics.free.fr/Deces-France.txt",
header=TRUE)
EXPO  <- read.table(
"http://freakonometrics.free.fr/Exposures-France.txt",
header=TRUE,skip=2)
library(gnm)
D=DEATH$Male
E=EXPO$Male
A=as.numeric(as.character(DEATH$Age))
Y=DEATH$Year
I=(A<100)
base=data.frame(D=D,E=E,Y=Y,A=A)
subbase=base[I,]
subbase=subbase[!is.na(subbase$A),]

The first idea can be to use a Poisson model, where the mortality rate is a smooth function of the age and the year, something like

that can be estimated using

library(mgcv)
regbsp=gam(D~s(A,Y,bs="cr")+offset(log(E)),data=subbase,family=quasipoisson)
predmodel=function(a,y) predict(regbsp,newdata=data.frame(A=a,Y=y,E=1))
vX=trunc(seq(0,99,length=41))
vY=trunc(seq(1900,2005,length=41))
vZ=outer(vX,vY,predmodel)
persp(vZ,theta=-30,col="green",shade=TRUE,xlab="Ages (0-100)",
ylab="Years (1900-2005)",zlab="Mortality rate (log)")

The mortality surface is here

It is also possible to extract the average value of the years, which is the interpretation of the  coefficient in the Lee-Carter model,

predAx=function(a) mean(predict(regbsp,newdata=data.frame(A=a,
Y=seq(min(subbase$Y),max(subbase$Y)),E=1)))
plot(seq(0,99),Vectorize(predAx)(seq(0,99)),col="red",lwd=3,type="l")

We have the following smoothed mortality rate

Recall that the Lee-Carter model is

where parameter estimates can be obtained using

regnp=gnm(D~factor(A)+Mult(factor(A),factor(Y))+offset(log(E)),
data=subbase,family=quasipoisson)
predmodel=function(a,y) predict(regnp,newdata=data.frame(A=a,Y=y,E=1))
vZ=outer(vX,vY,predmodel)
persp(vZ,theta=-30,col="green",shade=TRUE,xlab="Ages (0-100)",
ylab="Years (1900-2005)",zlab="Mortality rate (log)")

The (crude) mortality surface is

with the following  coefficients.

plot(seq(1,99),coefficients(regnp)[2:100],col="red",lwd=3,type="l")

Here we have a lot of coefficients, and unfortunately, on a smaller dataset, we have much more variability. Can we smooth our Lee-Carter model ? To get something which looks like

Actually, we can, and the code is rather simple

library(splines)
knotsA=c(20,40,60,80)
knotsY=c(1920,1945,1980,2000)
regsp=gnm(D~bs(subbase$A,knots=knotsA,Boundary.knots=range(subbase$A),degre=3)+
Mult(bs(subbase$A,knots=knotsA,Boundary.knots=range(subbase$A),degre=3),
 bs(subbase$Y,knots=knotsY,Boundary.knots=range(subbase$Y),degre=3))+
offset(log(E)),data=subbase, family=quasipoisson) 
BpA=bs(seq(0,99),knots=knotsA,Boundary.knots=range(subbase$A),degre=3) 
BpY=bs(seq(min(subbase$Y),max(subbase$Y)),knots=knotsY,Boundary.knots= range(subbase$Y),degre=3) 
predmodel=function(a,y) 
predict(regsp,newdata=data.frame(A=a,Y=y,E=1)) v
Z=outer(vX,vY,predmodel) 
persp(vZ,theta=-30,col="green",shade=TRUE,xlab="Ages (0-100)", 
ylab="Years (1900-2005)",zlab="Mortality rate (log)")

The mortality surface is now

and again, it is possible to extract the average mortality rate, as a function of the age, over the years,

BpA=bs(seq(0,99),knots=knotsA,Boundary.knots=range(subbase$A),degre=3)
Ax=BpA%*%coefficients(regsp)[2:8]
plot(seq(0,99),Ax,col="red",lwd=3,type="l")

We can then play with the smoothing parameters of the spline functions, and see the impact on the mortality surface

knotsA=seq(5,95,by=5)
knotsY=seq(1910,2000,by=10)
regsp=gnm(D~bs(A,knots=knotsA,Boundary.knots=range(subbase$A),degre=3)+
Mult(bs(A,knots=knotsA,Boundary.knots=range(subbase$A),degre=3),
bs(Y,knots=knotsY,Boundary.knots=range(subbase$Y),degre=3))
+offset(log(E)),data=subbase,family=quasipoisson)
predmodel=function(a,y) predict(regsp,newdata=data.frame(A=a,Y=y,E=1))
vZ=outer(vX,vY,predmodel)
persp(vZ,theta=-30,col="green",shade=TRUE,xlab="Ages (0-100)",
ylab="Years (1900-2005)",zlab="Mortality rate (log)")

We now have to use those functions our our small data sample ! That should be fun….

How old is the oldest person you know?

Last week, we had a discussion with some colleagues about the fact that – in order to prepare for the SOA exams – we did not have time (so far) to mention results on extreme values in our actuarial program. I did gave an introduction in my nonlife actuarial models class, but it was only an introduction, in three hours, in order to illustrate reinsurance pricing. And I told my students that if they wanted to know more about extreme values, they should start a master program in actuarial science and finance, since I will give a course on extremes (and copulas) next winter.

But actually, extreme values are everywhere ! For instance, there is a Prudential TV commercial where has people place large, round stickers on a number line to represent the age of the oldest person they know. This forms some kind of histogram. The message is to have Prudential prepare you to have adequate money for all these years. And actually, anyone can add his or her own sticker at the Prudential website.

Patrick Honner, on his blog (http://mrhonner.com/…), did mention this interesting representation. But this idea is not new, as mentioned in a post, published three years ago. In 1932, Emil Gumbel gave a talk in France on the “âge limite“. And as he wrote it “on peut donc supposer que la distribution de l’âge limite – c’est à dire la probabilité que cet âge ait une valeur donnée – soit Gaussienne“. In 1932 (not aware of Fisher and Tippett work, he thought that the limiting distribution for a maximum would be Gaussian). But a few years after, he read about Fisher’s work, and observed also that “la distribution d’une valeur extrêmes peut être représentée pour un nombre suffisant d’observations par la formule doublement exponentielle, pourvu que la distribution initiale se comporte asymptotiquement comme une exponentielle. La formule devient rigoureuse si la distribution initiale est exponentielle“, as he wrote in 1935. And in 1937, he wrote a paper on “les centennaires” that can also be related to the work of Bortkiewicz on rare events. One should also mention one of the most important paper in extreme value theory, published in 1974 by Balkema and de Haan, on Residual Life Time at Great Age.

Because in this experiment, the question is “How Old is the Oldest Person You Know?“, so it is the distribution of a maximum. And from Fisher-Tippett theorem, if we assume that the age is bounded (and that there exists some finite upper limit), then the limiting distribution for the maxima (or to be more rigorous, a affine transformation of the maxima) should be Weibull distribution. And this is what it looks like

> plot(-x,dweibull(x,2.25,4),type="l",lwd=2)

As an actuary, the only thing I know about demography, is the distribution of the age of death. For instance, consider the following French life table

> alive <- read.table(
+ "https://perso.univ-rennes1.fr/arthur.charpentier/TV8890.csv",
+ sep=";",header=TRUE)$Lx
> nb= -diff(alive)
> ages=0:110
> plot(ages,nb,type="h")

This is the distribution of the age of the death in a given population. Which is not the same as the distribution mentioned above! What we look for is the following: given that someone is alive, what could be the distribution of his-her age ? Actually, if we assume that the yearly number of birth is constant with time (as well as death probability), then we can compute easily to number of people of age https://latex.codecogs.com/gif.latex?x : we take everyone born (exactly) https://latex.codecogs.com/gif.latex?x years ago, and remove all those who died at at https://latex.codecogs.com/gif.latex?x, https://latex.codecogs.com/gif.latex?x-1, etc. So the function should be

> probadeath=nb/sum(nb)
> nbx=function(x) 1-sum(probadeath[1:(x+1)])
> surv=Vectorize(nbx)(ages)
> distrage=surv/sum(surv)

which looks like

But this assumption of constant number of birth is not that relevent. And actually, what we need is the distribution of the age within a population… This is a population pyramid, actually. The French one can be downloaded from http://www.insee.fr/fr/ppp/bases-de-donnees/….

> population <- read.table("popinsee2007.csv",sep=";",header=TRUE)$POPTOT07
> ages=0:107
> plot(ages,population/sum(population),type="h")

(the red line being the one obtained previously, using some natality assumptions). Now, let us use this population to generate acquaintances.

> agemax=function(nsim=1000,size=20){
+ agemax=rep(NA,nsim)
+ for(i in 1:nsim){
+ X=sample(ages,prob=population/sum(population),size=size,replace=TRUE)
+ agemax[i]=max(X)}
+ return(agemax)}

Here, we assume that everyone knows 20 other people, randomly chosen in the entire population, then we return the age of the oldest. And we do that for 1,000 people. Here is the distribution, we obtain

> XS=agemax(10000,20)
> plot(table(XS)/length(XS),type="h",xlim=c(0,108))

where the red line is a Weibull distribution (a transformed one, actually, since in extremely value theory, the distance to the upper bound of the distribution has a Weibull density),

> library(MASS)
> fit=fitdistr(108-XS,dweibull,list(shape=1,scale=1))
> lines(ages,dweibull(108-ages,fit$estimate[1],fit$estimate[2]),col="red")

Which is quite close to the distribution obtained in the commercial, don’t you think ? But still, it should be possible to be more accurate, since people should think of their parents, or grandparents. So I guess it could be possible to build a more accurate algorithm, to get something closer to the distribution obtained on the Prudential website. But first, let us wait to have more stickers, more observations… and then I’ll be back to play with it !

Combien de temps profite-t-on de ses grands parents ?

Ce Hier matin, je suis tombé un peu par hasard sur deux graphiques de l’INSEE (en France) avec l’age moyen des mères à l’accouchement, en fonction de rang de naissance de l’enfant, avec tout d’abord 1905-1965,

puis 1960-2000

Ces graphiques sont passionnants en soi – comme en ont témoigné pas mal de followers sur Twitter – mais ils m’ont fait m’interroger. En particulier, sur la croissance observée depuis 30 ans, qui me faisait penser à la tendance croissante observée sur les durées de vie. On n’a – malheureusement – pas accès au données complètes sur le site, mais on peut trouver d’autres donnéesintéressantes (en l’occurrence l’age moyen à la naissance).

> agenaissance=read.table("http://freakonometrics.blog.free.fr/
public/data/agenaissance.csv",header=TRUE,sep=",")
> agenaissance$Age=as.character(agenaissance$AGE)
> agenaissance$AGE=as.numeric(substr(agenaissance$Age,1,2))+
+ as.numeric(substr(agenaissance$Age,4,4))/10
> plot(agenaissance$ANNEE+.5,agenaissance$AGE,
+ type="l",lwd=2,col="blue")

Visuellement, on retrouve la courbe en bleu foncée sur les graphiques ci-dessus,

On peut alors aller en cran plus loin, en se demandant non pas quel était l’âge moyen de la mère, mais de la grand-mère (au sens la mère de la mère)

> agenaissance$NAIS.MERE=(agenaissance$ANNEE+.5)-
+ agenaissance$AGE
> w=(trunc(agenaissance$NAIS.MERE-.5))
> rownames(agenaissance)=agenaissance$ANNEE
> a1=agenaissance[as.character(w),]$NAIS.MERE
> a2=agenaissance[as.character(w+1),]$NAIS.MERE
> p=agenaissance$NAIS.MERE-(w+.5)
> agenaissance$NAIS.GRD.MERE=(1-p)*a1+p*a2
> agenaissance$age.GRD.MERE=agenaissance$ANNEE+.5-
+ agenaissance$NAIS.GRD.MERE
> tail(agenaissance)
ANNEE  AGE   Age NAIS.MERE NAIS.GRD.MERE age.GRD.MERE
2000  2000 30.3 30,3     1970.2       1942.87        57.63
2001  2001 30.4 30,4     1971.1       1943.80        57.70
2002  2002 30.4 30,4     1972.1       1944.92        57.58
2003  2003 30.5 30,5     1973.0       1945.95        57.55
2004  2004 30.5 30,5     1974.0       1947.05        57.45
2005  2005 30.6 30,6     1974.9       1948.04        57.46
> plot(agenaissance$ANNEE+.5,agenaissance$age.GRD.MERE,
+ type="l",lwd=2,col="red")

Là encore, on peut visualiser l’âge de la grand-mère maternelle à la naissance

A partir de là, on peut se demander combien de temps on profite de ses grands-parents (ou tout du moins ici de sa grand mère maternelle), en se basant sur les calculs d’espérance de vie résiduelle. En utilisant le modèle de Lee-Carter pour modéliser les taux de décès annuel, et en extrapolant sur le siècle en cours, on peut extrapoler les espérances de vie résiduelles.

> Deces <- read.table("http://freakonometrics.free.fr/
Deces-France.txt",header=TRUE)
> Expo  <- read.table("http://freakonometrics.free.fr/
Exposures-France.txt",header=TRUE,skip=2)
> Deces$Age <- as.numeric(as.character(Deces$Age))
> Deces$Age[is.na(Deces$Age)] <- 110
> Expo$Age <- as.numeric(as.character(Expo$Age))
> Expo$Age[is.na(Expo$Age)] <- 110
>  library(forecast)
>  library(demography)
>  YEAR <- unique(Deces$Year);nC=length(YEAR)
>  AGE  <- unique(Deces$Age);nL=length(AGE)
>  MUF  <- matrix(Deces$Female/Expo$Female,nL,nC)
>  POPF <- matrix(Expo$Female,nL,nC)
>  BASEF <- demogdata(data=MUF, pop=POPF,ages=AGE,
+ years=YEAR, type="mortality",
+  label="France", name="Femmes", lambda=1)
> LCF <- lca(BASEF)
> LCFf<-forecast(LCF,h=100)
> A <- LCF$ax
> B <- LCF$bx
> K1 <- LCF$kt
> K2 <- K1[length(K1)]+LCFf$kt.f$mean
> K <- c(K1,K2)
> MU <- matrix(NA,length(A),length(K))
> for(i in 1:length(A)){
+ for(j in 1:length(K)){
+ MU[i,j] <- exp(A[i]+B[i]*K[j]) }}
> esp.vie = function(xentier,T){
+ s <- seq(0,99-xentier-1)
+ MUd <- MU[xentier+1+s,T+s-1898]
+ Pxt <- cumprod(exp(-diag(MUd)))
+ ext <- sum(Pxt)
+ return(ext) }
> EVIE = function(x,T){
+ x1 <- trunc(x)
+ x2 <- x1+1
+ return((1-(x-x1))*esp.vie(x1,T)+(x-x1)*esp.vie(x2,T)) }
> agenaissance$EV=NA
> for(i in 1:100){
+ t <- 2006-i
+ agenaissance$EV[agenaissance$ANNEE==t]=
+ EVIE(x=agenaissance$age.GRD.MERE[
+ agenaissance$ANNEE==t],t) }
> tail(agenaissance)
ANNEE  AGE   Age NAIS.MERE NAIS.GRD.MERE age.GRD.MERE       EV
2000 30.3 30,3     1970.2       1942.87        57.63 29.13876
2001 30.4 30,4     1971.1       1943.80        57.70 29.17047
2002 30.4 30,4     1972.1       1944.92        57.58 29.39027
2003 30.5 30,5     1973.0       1945.95        57.55 29.52041
2004 30.5 30,5     1974.0       1947.05        57.45 29.72511
2005 30.6 30,6     1974.9       1948.04        57.46 29.80398

Autrement dit, sur la dernière ligne, l’espérance de vie (résiduelle) pour une femme de 57.46 ans en 2005 était d’environ 29.80 ans. On peut alors visualiser non seulement l’âge moyen de sa grand-mère à la naissance, mais son espérance de vie résiduelle,

> plot(agenaissance$ANNEE+.5,agenaissance$EV,
+ type="l",lwd=2,col="purple")

On note que depuis 30 ans, en France, la durée (moyenne) pendant laquelle les petits-enfants vont profiter de leur grands parents s’est stabilisé à une trentaine d’années. On peut aussi continuer, et remonter d’un cran (en refaisant tourner le code avec quelques modifications): on a alors l’âge (moyen) de son arrière grand mère à la naissance,

et la durée de vie (résiduelle) des arrière grand mères

On manque ici de données, mais il semble que l’on profite – en moyenne – environ 5 ans de son arrière grand mère. Maintenant on peut aussi s’interroger sur les limites de cette étude rapide. En particulier, de même qu’il existe une corrélation forte entre les durées de vie de conjoints (e.g. broken heart syndrom de Jagger & Sutton (1991)), on peut se demander si la naissance d’enfants et de petits-enfants a un impact sur la durée de vie résiduelle d’une personne (ou si on peut supposer l’indépendance comme on l’a fait ici).