The Spatial side of Demography at EPC…

Come meet me at EPC to discuss Spatial Demography!

Thursday, 7 June 2018, 9:00-10:30 Session 1 Motherhood, Labor Market and Wages: Contextual Determinants of Childbearing in Spain: A Spatial Panel Study

Friday, 8 June 2018, 11:00-12:30 Session 65 Fertility Trends and ProspectsThe Geography of Fertility Rates in Low and Middle-Income Countries: Analysis of Cross-Sectional Surveys from 74 Countries

Using Rodriguez and Trussel (1981) formula to compute Desired Fertility

Comparison between desired family size obtained through Rodriguez and Trussel’s (1981) formula and that from the Fertility and Family Survey.

Rplot

The gap between desired and observed fertility in Europe. Part 2: Childlessness levels.

To better understand the effect of postponement we tried to measure it by calculating the effect of time spent on contraception while in a union by women who want to have children, a ‘conscious’ way to postpone childbearing.

Involuntary childlessness has gained momentum in mainstream media, which attribute a large part (if not the totality) of the blame on the postponement of childbearing: women wait too long to have children, they don’t hear their biological clock ticking and bam! no children. Ever.

Delaying childbearing to later ages has undoubtedly a repercussion on the biological ability to have children, but it is hardly a simple component of the total effect. What the mainstream discussion is often missing on is that the great majority of children are conceived in unions, hence it is a couple’s decision to have children. Indeed, being single is an important if not pivotal deterrent to motherhood, usually delayed until union formation.

This is why it is important to consider factors such as union dissolution risk to appreciate the variation in involuntary childlessness. To better understand the effect of postponement we tried to measure it by calculating the effect of time spent on contraception while in a union by women who want to have children, a ‘conscious’ way to postpone childbearing.

This is a preview of average population childlessness obtained through simulation using 3 variables: celibacy (%of women ending up single and never entering a union), divorce (%women previously in a union but currently without a partner), and waiting time, the average time spent on contraception at the beginning of a union by a woman who wishes to have children.

childlessness

>ggplot(dt, aes( Age, value, linetype=Variable, col=Variable))+
> geom_line( size=1) +
> scale_color_manual( values=c( "black", "#666666", "grey","black", "#666666", "grey"), guide=guide_legend( nrow=3, byrow=F, title =  "Childlessness" )) +
> xlab("")+
>ylab("")+
>scale_linetype_manual( values=c("solid", "solid",  "solid", "twodash", "dotted", "dashed"), guide=guide_legend( nrow=3, byrow= F, title =  "Childlessness" ))+
>theme( plot.margin= unit(c(1,4,1,1), "cm"), legend.position="bottom", legend.direction= "vertical")

1. ggplot(dt, aes( Age, value, linetype= Variable, col=Variable))

linetype= Variable and col=Variable set in the aes tell ggplot to automatically divide the lines based on the number of Variable(s);

2. scale_color_manual sets the colors of the lines contained in values. I was not satisfied with what I got with scale_color_grey so I set my colors manually (_manual!);

3. since I want the legend at the bottom AND in two columns (or 3 rows) AND I have two features specified in the aes I need to add a guide=guide_legend(nrow=3) to each scale_blablabla_manual (that is to say scale_color_manual AND scale_linetype_manual);

4. In guide=guide_legend the byrow=F means that I do not want the legend to appear ordered by row, but rather by columns;

5. in theme( legend.position=”bottom”) tells ggplot to put the legend below the graph and legend.direction to plot it in a vertical way (which I divide in 3 rows)

A space-time box plot of Spain’s TFR for 910 comarcas.

The idea behind spatial analysis is that space matters and near things are more similar: a variable measured in city A is (ideally) different from the same variable measured in city B. A simple way to get a feeling and to represent this hypothesis is through graphical visualization, usually a map(s).

TFRG_all_4years_Spain

However, when dealing with time series maps are cumbersome and  with sometimes some information is lost, such as the national average or path convergence. Box plots are a simple yet very effective way to synthesize a lot of information in one graph. The following plot depicts TFR over a 30 years period for 910 Spanish areas with respect to the national average value (thick black line in the middle of the boxes).

p <- ggplot(dat, aes(x=factor(YEAR), y=dat$TFR))
p <- p + geom_boxplot()
p <- p + scale_y_continuous(limits=c(0,2.5)) + scale_x_discrete("YEAR", breaks=seq(1981,2011,by=5))

TFRG

Location, location, location! Why space matters in demography and why we should care.

Read my first contribution to the Demotrends blog! and don’t forget to like Demotrends either in facebook or twitter 🙂
Of course all graphics have been realized in R (maptools library and a bunch of others).
Location, location, location! Why space matters in demography and why we should care..