Restrictions and Measure vs Dimension
The thing that always bothered me about the wealth vs life expectancy presentation is that is never once highlights the impacts of the very strong influence of Infant Mortality Rate and whether or not a lower bound is included (i.e. of people who survive past infant mortality cut-off age...THIS is the avg. life expectancy)...of course this could be highlighted using ranges and medians as well
IMHO time-dependent measures should be primarily considered as a dimension/segmentation as opposed to a KPI. For instances, one of my clients wanted to know "avg age, in months, that a customer has been with registered with us" which is obviously always INCREASING if the bulk of acquisitions are historic or DECREASING if bulk are happening in more recent periods...very difficult for people to get their heads around that so better to segment as "New", "1-3 Months",...,"12 Months+", for instance. Especially if the chart itself has a time axis. (yes, yes in a proportional sense the same issue arises but at least you can SEE that influence and for non-proportional KPI's, gives far better insight)
Great presentation and obviously a man with great and respectable/enviable passion but that twist ending of "but here's what you should consider of the underlying data" would have been nice.