Click on the chart and use the left and right arrow keys to move along a band, and the up and down arrow keys to move between bands. Each point announces its own value, the height of the whole stack at that year, and what share of it this band is — the second magnitude a stacked area draws that a line reading would collapse away. Press B for braille, T for text descriptions, and S to toggle sonification.
Change stackMode('value') to stackMode('percent')
to read the same data as shares of a common total, or remove the call
entirely to read the three bands independently.