The Greatest Graphs in History.

In 1736, Leonard Euhler created what’s considered the first example of graph theory, when he identified the solution to the Seven Bridges of Königsberg problem. Since then, graphs have recorded and accentuated some of history’s most significant events; from wars to epidemics. Even a quick google search unearths a plethora of examples. While there is plenty to choose from, what is the greatest graph in history?

To answer this question, we start with 3 charts, considered by many as among the most important in history:

First we have Charles Minard’s 1869 graph of Napoleon’s 1812 march on Moscow which shows the effect of dropping sub-zero temperatures on Napolean’s army. The broad line on top represents the army’s size on the march from Poland to Moscow. The thin dark line below represents the army’s size on the retreat. The width of the lines represents the army size, which started over 400,000 strong and dwindled to 10,000. The bottom lines are temperature and time scales, and the overall plot shows distance traveled.

Next up, we have John Snow’s map of the 1854 cholera outbreak in London. John Snow supported his then controversial theory that cholera spread through contaminated water by marking each street as a line and representing the number of deaths within a specific household as a black bar, and by juxtaposing the location of the water pump on each street with dots. Once officials (reluctantly) shut down the Broad Street well, the epidemic subsided.

Finally, we have this time-series graph from William Playfair who is no slouch when it comes to graphs. Playfair invented some of the most commonly used charts in business including the line chart, bar chart, and the pie chart. As a political economist, Playfair used this chart below to show the economic progress of England using import/export numbers relative to Denmark and Norway. Over time, England began exporting more leading to a positive trade balance.

Each of these graphs represent a different genre (war, disease, and economics in that order) but all of them were ground-breaking for their time and told a clear and compelling story using data. But which of these graphs is the greatest? From our perspective, John Snow’s chart of the London cholera outbreak best represents the power of data visualization because it:

1. captured a complex set of metrics in one view (# deaths, relative comparison of households, proximity to water pumps etc.)
2. used a chart type that pulled together all the relevant data with the right context (impact of water pump location on household death)
3. highlighted a cause-effect relationship without any complex math or statistics (house holds closest to the water pumps suffered greater # of deaths)
4. provided a practical future solution to a current real world problem (shutting down of water pumps to limit cholera spread), and ultimately
5. saved an untold number of lives (once the city shut down the water pumps, the outbreak subsided)

The case for John Snow’s chart is even more compelling particularly considering the threat of Covid-19 we are all facing today. The disease has so far caused more than 42,000 deaths in the US, and more than 170,000 deaths worldwide. The pandemic has shut down the global economy, unleashing chaos on businesses and households. At the time of writing, oil is trading at -$40 per barrell and more than 22M Americans are unemployed. By any measure, Covid-19 will leave an indelible mark on world history. When history is written of the current era, “flatten the curve” will be the defining graphic of the pandemic. The idea is simple: Taking steps like washing your hands or staying home if you’re sick can slow down new cases of illness, so that the finite resources of our healthcare system can handle a more steady flow of sick patients rather than a sudden deluge.

The first instance of “flatten the curve” can be found in a CDC paper published in 2007. It suggested simple interventions like social distancing and keeping kids home from school in order to slow the spread of a disease so that the healthcare system could keep up. The chart was first popularized in the Covid era by the economist which published a briefing in Feb 2020, advocating for strategies to mitigate the spread of disease.

No one at the CDC has been able to identify the author of the original “flatten the curve” chart. But regardless of its authorship, this chart has already proved invaluable in many ways:

1. as an essential tool to educate the public and encourage compliance with social distancing guidelines
2. as a way to monitor localities to evaluate disease preparedness
3. as a framework for governments to issue and revoke stay at home guidelines

There is no doubt future historians and math enthusiasts will add the Covid-19 chart to the top of their list for the most famous charts in history. Whether John Snow’s cholera chart or the CDC’s Covid chart, they are not just great examples of the power of data-driven storytelling. They are also the perfect time capsule of their era, capturing the defining issue of their times in a powerful way and saving thousands of lives in the process.

To paraphrase, data is not the new oil. It’s the new vaccine.