Data Visualization and Cholera: An Unexpected Connection
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Data Visualization and Cholera: An Unexpected Connection

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Radial chart london cholera

Data Visualization and Cholera: An Unexpected Connection

Necessity is the mother of invention, and in the mid-1800s, understanding the spread of cholera was a matter of life and death.

Ruthless Efficiency

Cholera was a ruthlessly efficient killer, with both rapid onset and severe symptoms. By the time the disease made its way to London and New York in the early 1830s, hundreds of thousands of people had died across Europe, Africa, and Asia.

Not only our personal and national interests, […] it may be said without exaggeration, [that cholera] concerns the whole human race.

– Thomas Whiteside Hime

Needless to say, the human race was concerned. Thanks to high-speed printing press technology, daily newspaper circulations were rising dramatically, and this allowed journalists to experiment with new reporting techniques, including charting data.

cholera line chart

At the time, the chart above was such a novel approach that it required four paragraphs to explain how to read it. People of that era were simply not used to seeing data in a visual form. At a glance though, the chart is extremely effective at communicating a grim message: cholera had ravaged New York City over the summer of 1849.

Despite the concerted push to eradicate the disease, the medical community was still largely in the dark about how to prevent future outbreaks. Because doctors could treat numerous patients without falling ill, it was assumed that a miasmic environment (i.e. slums, densely-packed housing) was causing the spread.

Data Viz in the Time of Cholera

Today, we have tools that allow us to map just about anything, but in the mid-1800s, mapping data was still an innovative concept.

As early as the 1830s, geographers began using spatial analysis to study cholera epidemiology. The heat map below shows which sections of Paris were hardest hit by a recent outbreak of cholera.

1832 cholera map paris

In 1854, Dr. John Snow was convinced that cholera was spreading via tainted water and decided to display neighborhood mortality data directly on a map. This method clearly revealed a cluster of cases around a specific pump.

john snow cholera map
View the full version of the map here

The result is one of the most influential maps in modern history.

In addition to the real-world utility the map provided in helping physicians understand how cholera was spreading, it also exemplified a seismic shift in thinking that opened up new avenues for data to be analyzed and displayed.

Despite the tragic circumstances of the time period, we can be thankful that the urgency of the situation allowed the world’s pioneering researchers, journalists, and physicians to experiment with new data visualization techniques to better understand the world.

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Misc

Iconic Infographic Map Compares the World’s Mountains and Rivers

This iconic infographic map is an early and ambitious attempt to compare the world’s tallest mountains and longest rivers.

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Today, highly detailed maps of our planet’s surface are just a click away.

In times past, however, access to information was much more limited. It wasn’t until the 1800s that comparison diagrams and maps became widely accessible, and people found new ways to learn about the world around them.

The image above, published by J.H. Colton in 1849, is believed to be the first edition of the iconic mountains and rivers infographic map. This comparison chart concept would see a number of iterations over the years as it appeared in Colton’s world atlases.

Inspiring a Classic Infographic Map

A seminal example of this style of infographic was produced by Alexander von Humboldt in 1805. The diagram below is packed with information and shows geographical features in a way that was extremely novel at the time.

Alexander von Humboldt mountain diagram

In 1817, the brothers William and Daniel Lizars produced the first comparative chart of the world’s mountains and rivers. Breaking up individual natural features into components for comparison was a very innovative approach at that time, and it was this early French language prototype that lead to the Colton’s versions we’re familiar with today.

Digging into the Details

As is obvious, even at first glance, there is a ton of detail packed into this infographic map.

Firstly, rivers are artificially straightened and neatly arranged in rows for easy comparison. Lakes, mountain ranges, and cities are all labeled along the way. This unique comparison brings cities like New Orleans and Cairo side by side.

detailed view of longest rivers visualization

Of course, this visualization was based on the best available data at the time. Today, the Nile is widely considered to be the world’s longest river, followed by the Amazon and Yangtze.

Over on the mountain side, there are more details to take in. The visualization includes volcanic activity, notes on vegetation, and even the altitude of selected cities and towns.

detailed view of tallest mountains visualization

Above are a few of South America’s high-altitude population centers, including La Paz, which is the highest-elevation capital city in the world.

In the legend, many of the mountains are simply named “peak”. While this generic labeling might seem like a throwback to a time when the world was still being explored, it’s worth noting that today’s second tallest mountain is still simply referred to as K2.

What details do you notice while exploring this iconic infographic map?

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Demographics

Mapped: A Decade of Population Growth and Decline in U.S. Counties

This map shows which counties in the U.S. have seen the most growth, and which places have seen their populations dwindle in the last 10 years.

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A Decade of Population Growth and Decline in U.S. Counties

There are a number of factors that determine how much a region’s population changes.

If an area sees a high number of migrants, along with a strong birth rate and low death rate, then its population is bound to increase over time. On the flip side, if more people are leaving the area than coming in, and the region’s birth rate is low, then its population will likely decline.

Which areas in the United States are seeing the most growth, and which places are seeing their populations dwindle?

This map, using data from the U.S. Census Bureau, shows a decade of population movement across U.S. counties, painting a detailed picture of U.S. population growth between 2010 and 2020.

Counties With The Biggest Population Growth from 2010-2020

To calculate population estimates for each county, the U.S. Census Bureau does the following calculations:

A county’s base population → plus births → minus deaths → plus migration = new population estimate

 
From 2010 to 2020, Maricopa County in Arizona saw the highest increase in its population estimate. Over a decade, the county gained 753,898 residents. Below are the counties that saw the biggest increases in population:

RankCountyPoint of ReferenceStatePop. Growth (2010–2020)
#1Maricopa CountyPhoenix, ScottsdaleArizona+753,898
#2Harris CountyHoustonTexas+630,711
#3Clark CountyLas VegasNevada+363,323
#4King CountySeattleWashington+335,884
#5Tarrant CountyFort Worth, ArlingtonTexas+305,180
#6Bexar CountySan AntonioTexas+303,982
#7Riverside CountyRiverside, Palm SpringsCalifornia+287,626
#8Collin CountyPlanoTexas+284,967
#9Travis CountyAustinTexas+270,111
#10Hillsborough CountyTampaFlorida+264,446

Phoenix and surrounding areas grew faster than any other major city in the country. The region’s sunny climate and amenities are popular with retirees, but another draw is housing affordability. Families from more expensive markets—California in particular—are moving to the city in droves. This is a trend that spilled over into the pandemic era as more people moved into remote and hybrid work situations.

Texas counties saw a lot of growth as well, with five of the top 10 gainers located in the state of Texas. A big draw for Texas is its relatively affordable housing market. In 2021, average home prices in the state stood at $172,500$53,310 below the national average.

Counties With The Biggest Population Drops from 2010-2020

On the opposite end of the spectrum, here’s a look at the top 10 counties that saw the biggest declines in their populations over the decade:

RankCountyPoint of ReferenceStatePop. Growth (2010–2020)
#1Cook CountyChicagoIllinois-90,693
#2Wayne CountyDetroitMichigan-74,224
#3Cuyahoga CountyClevelandOhio-50,220
#4Genesee CountyFlintMichigan-20,165
#5Suffolk CountyLong IslandNew York-20,064
#6Caddo ParishShreveportLouisiana-18,173
#7Westmoreland CountyMurrysvillePennsylvania-17,942
#8Hinds CountyJacksonMississippi-17,751
#9Kanawha CountyCharlestonWest Virginia-16,672
#10Cambria CountyJohnstownPennsylvania-14,786

The largest drops happened in counties along the Great Lakes, including Cook County (which includes the city of Chicago) and Wayne County (which includes the city of Detroit).

For many of these counties, particularly those in America’s “Rust Belt”, population drops over this period were a continuation of decades-long trends. Wayne County is an extreme example of this trend. From 1970 to 2020, the area lost one-third of its population.

U.S. Population Growth in Percentage Terms (2010-2020)

While the map above is great at showing where the greatest number of Americans migrated, it downplays big changes in counties with smaller populations.

For example, McKenzie County in North Dakota, with a 2020 population of just 15,242, was the fastest-growing U.S. county over the past decade. The county’s 138% increase was driven primarily by the Bakken oil boom in the area. High-growth counties in Texas also grew as new sources of energy were extracted in rural areas.

The nation’s counties are evenly divided between population increase and decline, and clear patterns emerge.

population changes in u.s. counties (%)

Pandemic Population Changes

More recent population changes reflect longer-term trends. During the COVID-19 pandemic, many of the counties that saw the strongest population increases were located in high-growth states like Florida and Texas.

Below are the 20 counties that grew the most from 2020 to 2021.

RankCountyPoint of ReferenceStatePop. Growth (2020–2021)
#1Maricopa CountyPhoenixArizona+58,246
#2Collin CountyPlanoTexas+36,313
#3Riverside CountyRiverside, Palm SpringsCalifornia+35,631
#4Fort Bend CountySugar LandTexas+29,895
#5Williamson CountyGeorgetownTexas+27,760
#6Denton CountyDentonTexas+27,747
#7Polk CountyLakelandFlorida+24,287
#8Montgomery CountyThe WoodlandsTexas+23,948
#9Lee CountyFort MyersFlorida+23,297
#10Utah CountyProvoUtah+21,843
#11Pinal CountySan Tan ValleyArizona+19,974
#12Clark CountyLas VegasNevada+19,090
#13Pasco CountyNew Port RicheyFlorida+18,322
#14Wake CountyRaleighNorth Carolina+16,651
#15St. Johns CountySt. AugustineFlorida+15,550
#16Hillsborough CountyTampaFlorida+14,814
#17Bexar CountySan AntonioTexas+14,184
#18Ada CountyBoiseIdaho+13,947
#19Osceola CountyKissimmeeFlorida+12,427
#20St. Lucie CountyFort PierceFlorida+12,304

Many of these counties are located next to large cities, reflecting a shift to the suburbs and larger living spaces. However, as COVID-19 restrictions ease, and the pandemic housing boom tapers off due to rising interest rates, it remains to be seen whether the suburban shift will continue, or if people begin to migrate back to city centers.

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