USA Population Change

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Why we love it

We love how colour and 3D shading work together to tell the story of US population changes from 2000 to 2010. Declining counties show up in red and shrink into the map. Growing counties pop in green and literally burst from the screen. As a bonus, you can zoom into a city to reveal more spatial details and discover changes in a particular neighborhood.

Why it works

What really makes this map useful (and smart) is the 3D shading compares nearby places using relative height. 3D especially showcases meaningful and even subtle differences within each colour. For example, red simply tells us places are shrinking in population, but shading gives us relative-depth cues to indicate wide differences in losses within that category. 

Important steps

  • Select time period data

    You will need population data for two different time periods such as 2000 and 2010.

  • Use diverging colour scheme

    Map the data using a diverging colour scheme (known in ArcGIS Online as “above and below”), and make the middle colour neutral, centered on 0 or “no change.”

  • Evaluate and publish your map

    Evaluate the results in ArcMap or ArcGIS Pro. Publish as a tiled map service to ArcGIS Online.
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Requirements

  • Data and software

    You need numerical data — it could be income, housing prices, life expectancy, anything that shows change over time. Maps like this work best with data that is a rate, ratio, percent, index, or average, and changes over time. Software used: ArcGIS Desktop, ArcGIS Online.

  • Analysis

    Think about how to show growth and decline in population. Here, zero growth is a neutral colour and growth rates are shaded in diverging colors. The Python tool analyses growth rates to determine height and shading for each feature.

  • Time

    The first time you do this it will take about one day for setup, one day for processing, and one day for caching.
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Tips and tricks

  • Emphasise with colour sequence

    Use an above-and-below colour sequence when you have a meaningful midpoint in your data that you want to emphasise, such as zero or an average.

  • Place light source in upper left

    When adding shadows, it looks more natural if you place the light source in the upper left, at the 10 or 11 o’clock position.
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Resources

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Wesley Jones, geographer and mapmaker

Map Author

Wesley Jones

Mapmaker, mapmaker, make me a map. I am a geographer and mapmaker. I like illustrating and writing. I also enjoy the sport of curling.

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