One dot per country, placed on a life-expectancy axis and laned by region.
plotOptions.unit.layout: 'scatter' places each unit on a numeric
X value axis by its own value, laned by category on Y, and draws the axis +
lanes itself. scatter.spread: 'swarm' packs equal / close values
off the centre line with no overlap, so the lane becomes a density silhouette
(not the blur of a random jitter). Switching the year is a plain
chart.updateSeries(), so every country dot tweens to its new
place. The unit chart is a premium type; without a license it renders with a
trial watermark. Figures are approximate (public-health style).