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).
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))