Color Me Curious: Why PolicyMap Maps are Purple

Data visualization is a powerful tool—colors can provide very meaningful context, but they can just as easily make for a very misleading representation of your information. There are a few things to think about when choosing colors to symbolize your data, namely, color properties, connotations, and relationships to other objects or features on the ground.


Munsell’s cylindrical arrangement of colors: the horizontal line represents chroma (saturation), the vertical line represents value (lightness) and the circle represents hue.

The technical portion of color choice deals with how colors are interpreted by the human eye, and how they look on our computer screens. Colors have three distinct properties: hue (the name of the color), value (lightness or darkness), and saturation (brightness or dullness). Because colors have these intrinsic qualities, we are able to use variations on these properties to give meaning to our data. This means that rather than using a spectral (rainbow) color scheme to represent information, we can provide color gradients to allow people to see gradual changes. Rainbow colors are not necessarily bad when used for categorical data, such as types of program eligibility, but seem nonsensical when used to represent continuous data (i.e. temperature, or crime rates).

Some colors are more difficult to see and distinguish than others (yellow, for example), while other colors might seem to make a statement about your data (red, for instance, may imply something bad). It is also important to remain aware of relationships with other map features, which is why displaying data as blue or green (colors typically used for bodies of water or parks) could make it more difficult for someone to differentiate between said features.

At PolicyMap, we use purple as the default setting for our maps. This isn’t due to branding, or to our love for singer-songwriter Prince, rather, we use purple because it is an attractive and non-deceptive way to represent a broad range of datasets. We can also use supplementary colors to strengthen our visualizations; here at PolicyMap we often use the color orange to display negative values.

Use the map below to take a look at how we represent population change in purple and orange. In this case, the saturation of each color reflects the estimated percent rise or decline of population.

There are myriad ways to display information on a map, and we hope that this brief introduction to color and visualizations has provided some helpful pointers to help you choose how best to represent your own data! For a more complete discussion, check out our Mapchat: The Art of Making Maps.


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It’s a SNAP… Affordable, Farm-Fresh Produce!

It’s National Farmers’ Market Week! To us here at PolicyMap, farmers’ markets are more than a place to pick the perfect summer tomato. As direct farm-to-consumer sales locations, farmers’ markets connect shoppers to the agricultural systems that grow our fruits, vegetables, and proteins.

Farmers MarketsIncreasingly, farmers’ markets are growing more accessible to low-income consumers. As of 2015, 27 percent of farmers’ markets accept SNAP (Supplemental Nutrition Assistance Program) benefits. Formerly known as food stamps, SNAP is a federal program that allows low-income and unemployed persons to purchase food. Though most supermarkets accept SNAP, many of the locations accepting benefits are corner stores, mini-marts, and other small locations not known for their fresh produce. In areas where food options are limited, farmers’ markets can be an important source of nutrition for low-income people. The map below shows the rate of SNAP-Authorized stores per person, with the locations of farmers markets accepting SNAP:

Farmers’ markets present many challenges to low-income shoppers. They are often open only one day per week, and some may not be transit accessible. Additionally, the cost of farm-fresh food can be high, and is sometimes out of reach for those on a tight budget. Many farmers’ markets and other food retail locations are now able provide financial incentives that increase the value of SNAP benefits, thanks to Food Insecurity Nutrition Incentive grants, a new USDA program. This program allows SNAP recipients to supplement their food budget with additional fruits and vegetables.

Data on SNAP benefits and farmers’ markets are also updated on the Healthy Food Access Portal Research Your Community interactive mapping tool, where you can learn more about how farmers’ markets fit into local food access strategies.

Market photo by flickr user Phil Roeder
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Mapchats – The Art of Maps

The Art of Maps

Data is the key to maps. But show that data in a confusing, unattractive, or misleading way, and the power of your data is lost. Normally, Mapchats focus on using good data, but this time we focus on the nuts and bolts of making good maps.

PolicyMap’s popular Mapchats series continued 7/28/15 with a panel of leaders in online mapping, including Robert Cheetham from Azavea, Jake Garcia from Foundation Center, and PolicyMap’s own Bernie Langer. The topics of discussion include picking the right colors for a map, choosing the right map for the right data, and how to make a good map show change over time.
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Winner of the First #DataWiz Contest!

We just wrapped up our first DataWiz contest and wow, the responses definitely set the bar high. We received submissions in the form of tweets, emails, Census FIPS codes, and even original maps. It was, in a word, impressive.

In case you didn’t catch the quiz question, we asked, “What are the most racially diverse places in the U.S.?” Granted, this was an open-ended question and that was intentional on our part. We know that diversity and place can be interpreted in a number of different ways: is diversity most meaningfully measured at the scale of a neighborhood? County? City? The responses definitely reflected this variety. Some people gave the name of a neighborhood, a Census tract ID, or the name of a county.

We defined the answer as: the county containing the Census tract with the highest diversity index value and we used race and ethnicity data from the American Community Survey 2009-2013 5-year averages. The correct answer turned out to be Anchorage, Alaska, meaning that there were actually two winners: Philly’s own Jake Riley and Twitter user @bomberterp. Congratulations to you both!

Both winners will receive some classy PolicyMap swag. Extra nerd points go out to Jake for also submitting a map of the top 10 most diverse tracts and for describing his methodology. Well done!

In case you’re curious, the Census FIPS code of the most diverse tract is: 02020000901. Not far behind were tracts in Queens, NY, Pierce County, WA and Honolulu, HI.

Stay tuned for the next #DataWiz contest!

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Looking for the Local Boundaries?

You might have noticed that our Map Boundaries menu has been cleaned up a bit. We have removed the Local Boundaries menu. As the name implies, these boundaries are mainly localize boundaries and can only be seen if you are in the city or state that they represent which was why we have removed them for all users.

Local Boundaries

We have only removed them from display so don’t worry, they are still there and can be added to your account easily. Below is the list of available Local Boundaries (in alphabetical order) that can be added to your account;
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Americans with Disabilities Act Turns 25

This upcoming Sunday, July 26th marks the 25th anniversary of the signing of the Americans with Disabilities Act (ADA) by President George H.W. Bush.  Since its signing into law, the ADA has enabled millions of Americans with disabilities to participate in the workforce by removing legal barriers to employment. This landmark piece of legislation prohibits discrimination against people with disabilities within the workplace as well as in receiving services from federal, state, and local governments.

According to the US Census Bureau, in 2010, there were 56.7 million Americans with disabilities, representing 19 percent of the civilian non-institutionalized population.  Median earning for individuals with disabilities in the past 12 months is $20,885, amounting to 68 percent of overall median earnings, $30,928.

In 2014, 17.1 percent of individuals with a disability were employed and the unemployment rate for individuals with a disability decreased by 12.5 percent from 2013 to 2014. The United States Department of Labor Statistics notes most individuals with disabilities were employed in the education and health services, retail trade, professional and business services, and manufacturing industries.

PolicyMap has several indicators in the Demographics menu about individuals with disabilities. Featured below is the data by employment, displaying state-level data for individuals with disabilities who are employed in the workforce. Zoom in further to see the data displayed at more local levels.

Data mapped by PolicyMap, an online GIS mapping tool.
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July Data News – New Racial and Ethnic Segregation Data

New Racial and Ethnic Segregation Data

New Racial and Ethnic Segregation Data

Turn to PolicyMap for the latest data on racial integration in neighborhoods across the country. PolicyMap now provides an index of segregation that allows users to click on the map and instantly understand the level of segregation and the racial makeup of neighborhoods. Read More

See a complete list of new and updated datasets here!


Making Effective Visualizations

Mapchats continues next week with a panel of leaders in online mapping from Azavea, Foundation Center and PolicyMap, who will discuss the nuts and bolts of making beautiful and effective maps that tell a story.

July 28 | 3—4 PM EST


Test your knowledge of diversity data by entering our new Data Wizards (#DataWiz) contest!

Tell us which place in the U.S. you think is the most diverse by Sunday via Tweet (hashtag #DataWiz) or email, and winners will get a most special prize from PolicyMap.

Happy Mapping!
-Your friends at PolicyMap

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Think You Know Data? Show Your Skills In Our Data Wizards (#DataWiz) Contests

Knowing about data is just too much fun. Often, too much fun to just keep it to yourself. We know how you feel. Show off your nerd knowledge in our new series of #DataWiz contests!

We have officially announced our first #DataWiz contest, and it is well underway! The question is: What are the most racially diverse places in America? We’ve had great responses so far – keep them coming! Submit your answers by the stroke of midnight on Sunday, July 26th for a chance to win fame, glory, and even a prize from PolicyMap!

Answers can be submitted via Tweet with the hashtag #datawiz, email at, and why not, we’ll even accept snail mail for this one. Winners will be announced on the blog on Monday.


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The Art of Maps: Making Effective Visualizations

The Art of Maps

Data is the key to maps. But show that data in a confusing, unattractive, or misleading way, and the power of your data is lost. Normally, Mapchats focus on using good data, but this time we’ll focus on the nuts and bolts of making good maps.

Tuesday, 7/28 | 3 PM EST

PolicyMap’s popular Mapchats series continues next week with a panel of leaders in online mapping, including Robert Cheetham from Azavea, Jake Garcia from Foundation Center, and PolicyMap’s own Bernie Langer. The topics to be discussed will include picking the right colors for a map, choosing the right map for the right data, and how to make a good map show change over time.

Click here to save your seat!

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Racial and Ethnic Segregation: In the News and On PolicyMap

Residential segregation certainly has been making headlines over the past month. On June 25th, the Supreme Court rejected a challenge to the Fair Housing Act of 1968 in Texas Department of Housing and Community Affairs et al., v. Inclusive Communities Project, Inc. et al., thereby upholding the ability for advocates to quantitatively show that housing practices have a “disparate impact,” even if the original intent of these practices is not discriminatory.

On July 8th, President Obama and HUD Secretary Julian Castro introduced a new rule to “affirmatively further fair housing.” This rule comes after several years in the making and is most notable in that it:

“directs HUD’s program participants to take significant actions to overcome historic patterns of segregation, achieve truly balanced and integrated living patterns, promote fair housing choice, and foster inclusive communities that are free from discrimination” (source: HUD Final Rule).

Both of these rulings attempt to redress and redirect residential patterns of segregation; a widespread by-product of decades of race-based practices such as redlining, contract mortgages, segregated zoning ordinances, and the concentration of tax credits for public and affordable housing in low-income, urban, neighborhoods of color.

The new HUD rule-making also makes clear that a primary aim is to make data-driven analyses and decisions regarding fair housing more accessible. To achieve this goal, HUD is enhancing their existing online interactive mapping tool, where grantees of federal subsidies can assess if housing is, or potentially is not, being allocated in a fair manner across communities.

At the heart of PolicyMap’s work is a similar aim – to provide individuals and organizations the data they need to better understand the social, political, economic and environmental context of life. So, while it was several months in the making, PolicyMap is making a timely release of several indicators that may prove complementary in assessing “disparate impacts” in housing practices.

National Segregation Index
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