I stumbled across a chart that’s in my opinion the best way to express a comparison of quantities through time:
It compares the new PC companies, such as Apple, to traditional PC companies like IBM and Compaq, but on the same scale. If you’d like to see how iPads and other novelties compare, see here. I’ve tried to use the same type of visualization in my old work on legal data visualization.
It comes from a new market research firm Asymco that also produced a very clean income vs expenses visualization (click to enlarge):
While the first figure is pure perfection, Tufte purists might find the second one too colorful. But to a busy person, color helps tell things apart: when I know that pink means interest, it takes a fraction of the second to assess the situation. We live in 2012, not in 1712 to have to think black and white.
Finally, they have a few other interesting uses of interactive visualization, such as cellular-broadband infrastructure around the world through time – along with the underlying data. It seems that the GapMinder tools are now out there.