Steve McGourty offers this chart of US national debt by year, with the added feature of also indicating which president was bossing around that country in each time period.
This is a good example of a chart supporting an argument. Here, the argument is that the "common sense" notion that fiscal conservatism is the bailiwick of Republicans is flat out wrong, and the chart does a good job of illustrating this fallacy. However popular this chart might be , it could be a lot better, on both substantive and formal grounds.
Substantively, time-series economic data covering such a long range should be normalised for inflation; and some context (such as similarly-normalised GDP for the same time series) would be quite helpful. Here it turns out that the data still supports the argument when normalised and contextualised, so the evidence is strengthened by such refinements.
Formally, the scale labels on y-axis should have a lot fewer '0's; they might be intended to make an ancillary point about how large the US national debt is, but they distract from the essential core of this chart; a log scale for the y-axis would more aptly show the rate of change in the debt; and the overall look of the chart is faint and spindly, with thin lines and a very wide aspect ratio.
It is good to see some indication of the data source indicated right on the graphic, since that important information can often get lost as an image makes its way through the internet's many tubes.
 My Google search today turns up this chart's home as the second hit for United States National Debt.
This chart, titled "Booksthatmakeyoudumb" (and others like it that appear at "booksthatmakeyoudumb dot virgil dot gr", published by "virgil at caltech dot edu"), is a good example of a chart offering a facade of knowledge.
The author himself characterises the chart(s) as a bald grab for PageRank, "I seek Google linkage-love", and that seems to offer the most intelligent avenue for meaningful discussion about this chart and web page. Several points help with the quest for hits and links:
- connection to Facebook
- appearance of "analysis" leading to novel "results"
- appeal to intellectual vanity
- appeal to college esprit de corps
- colourful diagram
- opportunity for community