Mapping US Census Bureau Data in ArcGIS Pro

Demographic data is "the statistical characteristics of human populations (such as age or income)." Etymologically, the word is a combination of the Greek words dêmos (people) and graphein (write) - literally, writing about people (Merriam-Webster 2020). Typical demographic variables for an area include:

The US Census Bureau (USCB) is the part of the US federal government responsible for collecting data about people and the economy in the United States. The Census Bureau has its roots in Article I, section 2 of the US Constitution, which mandates an enumeration of the entire US population every ten years (the decennial census) in order to set the number of members from each state in the House of Representatives and Electoral College (USCB 2017).

This tutorial describes the steps for creating area maps from US Census Bureau Data in ArcGIS Pro.

  1. Start the Map
  2. Acquire the Data
  3. Subset the Data (Optional)
  4. Symbolize the Features
  5. Label the Features (Optional)
  6. Present the Map
  7. Save Your Project

The American Community Survey

Among the Census Bureau's many programs is the American Community Survey (ACS), an ongoing survey that provides information on an annual basis about people in the United States beyond the basic information collected in the decennial census. The ACS is commonly used by a wide variety of researchers when they need information about the general public.

Unlike the constitutionally-mandated decennial census which is only taken every ten years, the ACS continuously surveys people in America's communities so that the ACS data can be more detailed and current than the decennial census. However, because it is a survey rather than a complete count like the census, there is uncertainty about how accurately the sampling represents the facts on the ground, and that uncertainty is expressed in a statistical margin of error (MOE) on most ACS values (US Census Bureau 2018).

ACS data is released with data that is gathered over 1-year and 5-year intervals. The shorter intervals are more current, but less accurate, and often available only in a limted set of areas (like highly populous counties). The longer intervals are more accurate, but less current. You should choose the data set based on whether the analysis you are performing needs data that is more accurate or more up-to-date. For this tutorial, we go with accuracy by choosing the most recent five-year estimates.

The American Community Survey

Profile Pages on data.census.gov

The USCB's primary data portal is data.census.gov.

Although the portal provides a wide varity of types of access to the USCB's data, profile pages can be useful if you are looking for summary demographic and economic information about a specific area.

You can find these pages in data.census.gov by searching for a place name along with the word "profile."

The video below shows how to access the profile pages for the USA, Illinois, and Urbana, IL.

Viewing profile pages in data.census.gov

Start the Map

Start a New Project

To create a new map in a new project:

  1. Log in to ArcGIS Pro.
  2. When presented with options on the start screen, start your new project with a Map.
  3. Give the project a meaningful title so you can keep track of what is in different projects.
Starting a new project

Add a Map to an Existing Project

If you have an existing project you can add an additional map to the project by going to the Insert tab and selecting Map.

You may want to rename your maps so it is clear what map is what.

Adding a map to an existing project

Acquire the Data

Organizational Feature Service

Although data.census.gov is the definitive source for US Census Bureau data, the amount of available data is vast, and that data is made available in formats that requires additional processing to use in GIS. Accordingly, subsets of that data are sometimes made available within organizations in pre-processed forms to facilitate easier use.

The video below demonstrates how to add the Minn 2014-2018 ACS Counties feature service available from the University of Illinois ArcGIS Online organization.

Creating a county map using an organizational feature service

ESRI's Living Atlas

If you are not too particular about the symbology of your map ESRI's Living Atlas of the World contains a variety of layers of demographic data. Some of this data is from the American Community Survey, although ESRI also makes data available that they collect from other sources.

The video below shows how to add a Living Atlas layer of median age to a map in ArcGIS Pro. Note that this layer is scale-dependent and changes the types of areas being displayed (states, counties, census tracts) depending on how closely you are zoomed in to the map.

Creating a map using a Living Atlas feature service

Downloading Data From data.census.gov

The US Census Bureau makes a significant amount of their data available on data.census.gov. However, that data is only made available in tables. In order to map the data, you must join the data to polygons outlining the areas being represented in the data.

Data Tables data.census.gov

The video demonstrates how to download data tables from data.census.gov and prepare them for use in ArcGIS Pro using the Excel. This example uses median household income by county in Illinois.

  1. Go to data.census.gov and search for the variable you need. You may need to dig around for awhile or consider a substitute if what you are looking for is unavailable. In this example, B19013 Median Household Income is just what we're looking for.
  2. Select the type of geographic areas you are looking for. In this case we are looking at counties in Illinois. You may need to select Transpose Table to see all of your values.
  3. Make sure that you have the appropriate number of values. In this example, the 1-year estimates do not contain all counties, so we switch to the 5-year estimates. The 5-year data is almost always the better choice for county or local level data.
  4. Download the data as a CSV to your hard drive.
  5. Using Windows Explorer, navigate into the .zip archive file and copy the file that contains "data_with_overlays" to your desktop.
  6. Open that file in a spreadsheet program like Excel, remove the top row with cryptic names, and rename the variable column to something short but descriptive.
  7. IMPORTANT: Sort your data to find any non-numeric values and remove them.
  8. Save it back to your desktop as a CSV file.
Downloading a table from data.census.gov

Download A TIGER Cartographic Boundary Shapefile

The USCB maintains a collection of geospatial data on political boundaries in their Topologically Integrated Geographic Encoding and Referencing (TIGER) database.

They make a version of that data suitable for mapping as TIGER/Line cartographic boundary shapefiles.

Shapefiles utilize an old file format that ESRI developed in the 1990s. Despite their limitations (most notably limiting field names to ten characters), the format is supported by a wide variety of software, and is still commonly used to store and distribute geospatial data.

A shapefile is actually a collection of separate files that each contain separate information, such as the coordinates, attributes, projection, and metadata. Because all these files need to be kept together, shapefiles are commonly distributed in .zip archives that collect and compress the separate files into a single, compact file with .zip at the end of the name.

This video demonstrates how to download, unzip, and import a shapefile into ArcGIS Pro. This example uses county polygon boundaries compatable with the ACS data described above.

  1. Go to the USCB's TIGER Cartographic Boundary Shapefiles page and download the appropriate type of geography. The smaller (lower resolution) files are fine unless you are doing high accuracy mapping.
  2. Using Windows Explorer, find the downloaded .zip file and Extract All...
  3. Alternatively, you can double-click to open the file, and then copy the contents to your desktop.
Downloading and importing a shapefile into ArcGIS Pro

Join the Data Table with the Spatial Data and Symbolize

We now have a table of county-level data and a layer of features defining the boundaries of those counties. In order to map that data, we need to perform an attribute join.

A join is a database operation where two tables are connected based on common key values. In GIS, an attribute join is used to connect data from external tables (such as in a CSV file) to geospatial locations defined in a feature class that comes from a shapefile or file geodatabase.

Attribute join illustration

For the join key, we use the USCB number that is a field common to both the table downloaded from data.census.gov and the TIGER/LINE shapefile.

  1. Add Data from your computer and add the shapefile that has a .shp suffix.
  2. If needed, modify the projection to something cartographically valid like WGS 1984 Web Mercator.
  3. Right click on the layer, select Joins and Relates, and select Add Join.
  4. The Layer Name should be the polygon layer.
  5. The Input Join Field should be AFFGEOID.
  6. In Join Table, navigate to the spreadsheet you edited.
  7. The Output Join Field should be the id field from the spreadsheet.
  8. Uncheck Keep All Target Features so only the boundaries with matching entries in the data table are kept.
  9. Run the tool and you should have new fields joined to the polygon layer.
  10. Right click on the layer, and Export Features. This will copy the joined features to your project database so it will be saved with the project.
  11. Remove the original shapefile layer.
Joining in ArcGIS Pro

Subset the Data (Optional)

If using data from a feature service that covers a broad area, you may need to isolate particular subsets of the data.

For this example, we use a definition query to subset the feature service loaded earlier to only the counties in Illinois.

  1. TIGER files have different identification fields depending on the geography. With county-level data like this, the STATEFP field is a numeric code that indicates the state.
  2. Examine the fields in a location in the area you want to select to find the appropriate code. In this case, the STATEFP for Illinois is 17.
  3. Right click on the layer, select Properties and select Definition Query.
  4. Add a New Definition Query.
  5. Select the identification field (STATEFP), is equal to, and the identification code (17).
  6. Click OK and only the locations matching the criteria should be visible.
Isolating a subset of features

Symbolize the Features

Symbolizing Amounts: Graduated Colors

Data values that are measured or aggregated (such as averages or medians) can be visualized as choropleths, where the areas are colored based on the values. The range of colors used should clearly express a continuum of values, such as varying lightness or saturation of a single hue, or a spectrum between two hues.

A single hue choropleth

Symbolizing Amounts: Diverging Colors

When low and high values represent significantly different conditions, a diverging color scheme is commonly used where one color is used for low values, another for high values, and the two colors converge to a gray color in the middle.

A choropleth with a diverging color scheme

Symbolizing Counts

When mapping variables that are counts (such as population), graduated symbols should be used instead of graduated colors whenever there are significant differences in the spatial density of those counts. Population is a useful example because a choropleth of population will make low population counts in large western states see more dominant around the country than the small, densely populated states in the northeast and midwest.

A graduated symbol (bubble) map

Label the Features

Labels can be added if the areas leave space for legible text and if knowing the names or other characteristics about areas is important to the interpretation of the map.

However, labels can be distracting if the focus of the map is the spatial distribution of the phenomenon rather than knowing what specific areas have specific values.

Adding labels

Present the Map

Layout For a Figure

In order to use the map as a figure in a document (such as a report), you need to create a map layout.

  1. On the Insert tab, select New Layout. The size of the layout is dependent on how big you want it to be in your printed document. For this example we use 6" x 4".
  2. Add a map frame for the main mapping area.
  3. Size the map to 6 x 4 so it fills the figure and remove the frame line in case you do not want it in your document.
  4. Add a legend with a background and border so it stands out over the map.
  5. Add a Legend.
    1. Double click the variable name and give it a meaningful name that will look good in the legend.
    2. Remove the Layer Name from the legend so there is only one heading.
    3. Adjust the decimal points if needed.
  6. Create a dynamic text box outside of the figure to remove the the service credit for the base map.
  7. Add inset map frames for any outlying geographic regions. In the case of the US, Alaska and Hawaii are states that should be included on your maps of the country.
  8. Add a north arrow.
  9. Share -> Export to a PNG file. Portable Network Graphics is a file format that preserves quality at the expense of being larger than some other formats. Quality is important if you are printing.
  10. Insert the map in your Word document as a picture and center it.
  11. Give figure a meaningful caption. You can get source information by right-clicking on the layer and selecting View Metadata
Choropleth layout for a figure

Create a Print Layout For a Standalone Map

If you are going to use the map on its own, such as for a standalone handout or poster, you can add map elements to the layout to format the complete page.

  1. On the Insert tab, select Print Layout. For this example we use an 8.5" x 11" sheet of paper and choose Landscape orientation since the US is wider than it is tall.
  2. Add a map frame for the main mapping area.
  3. Add a legend and place it below the main mapping area.
    1. Double click the variable name and give it a meaningful name that will look good in the legend.
    2. Remove the Layer Name from the legend so there is only one heading.
    3. Adjust the decimal points if needed.
  4. Rename the layer as a meaningful title and remove the heading (variable name) so the text in the legend is relevant.
  5. Create a dynamic text box outside of the figure to remove the the service credit for the base map.
  6. Add inset map frames for any outlying geographic regions. In the case of the US, Alaska and Hawaii are states that should be included on your maps of the country.
  7. Add a textbox with a meaningful title.
  8. Add a north arrow.
  9. Add marginalia with the cartographer, date, and data source.
  10. Share -> Export to a PDF file. Portable Document Format preserves the layout exactly as you created it, regardless of what machine you view the file on.
Creating a standalone print layout

Publish the Data As A Service

If you want to share your data with others, or want to put it in an ArcGIS Online web map, you need to publish it as a feature layer.

  1. In the Contents pane, right click on the layer, select Data and Export Features. Because the joined exists only in the project, you need to export your joined layer as a completely new layer (feature class).
  2. Give the feature class a meaningful name. Note that this name should only contain letters (no spaces or punctuation marks)
  3. Run the tool.
  4. Change the symbology to color the layer by your variable.
  5. Right click on the new layer, select Sharing and Share as Web Layer.
  6. Give the layer a meaningful name, along with a summary.
Publishing a layer

Save the Project

Save A Project Package

When you are done with a project, you should save it as a project package on ArcGIS Online:

  1. This package will save all of your maps, layouts, and local data together so that you can reopen the package later on any computer if you need to modify or recreate any maps.
  2. You can share the package in case you want someone else to be able to use the materials you created in the project.
  3. Saving this to ArcGIS online will protect you from losing your data if something happens to your normal work computer.
Saving a project package to ArcGIS Online

Saving Failure

If you had any problems running tools during your session, your project may warn you about geoprocessing history problems and refuse to save.

The solution is to clear your geoprocessing history items.

Saving a project package to ArcGIS Online

Reopen a Project Package

Reopening a project from a project package

Cautions When Interpreting Census Data

Sampling Issues

Unlike the Decennial Census which attempts to collect information from everybody, the American Community Survey only gets information from a randomly selected group of people (a sample), and then uses statistical techniques to make an inference about the overall characteristics of the areas where those people live or work.

Because ACS data is a sample, we cannot be absolutely certain what the actual overall value really is. All ACS values have a margin of error that gives a range of possible values, usually with in a 95% level of confidence. These margins of error can be especially high in sparsely-populated rural areas, or with values that apply so small numbers of people.

While using ACS values as-is is usually fine for mapping, when your analysis involves high levels of accuracy or rigor, you need to be aware of the margins of error on your variables and communicate your uncertainty to your audience.

Aggregation Issues

Aggregated data is data that combines data from groups of individuals (often based on location in different geographic areas) into a smaller set of numbers, usually averages or medians. While the USCB collects data from individuals, it always aggregates that data by geographic areas to preserve anonymity and privacy.

As with sampling, aggregation introduces uncertainty as important individual distinctions can be lost when people are combined into groups and summarized.

One issue with aggregated data is the ecological fallacy, when you make assumptions about individuals based on aggregated data. For example, states are often classified as red states or blue states based on whether the majority of the voters in that state vote Republican or Democratic, respectively. However, even in very red Utah, Democratic President Obama got 25% of the vote in the 2012, so assuming that everyone you meet in Utah is conservative is incorrect.

2012 Electoral College Results Choropleth

The opposite of the ecological fallacy is the exception fallacy, where an assumption is made about a group based on a few exceptional individuals. For example, if you meet a tall basketball player from Ohio, the assumption that everyone in Ohio is tall would be incorrect.

LeBron James with the Cleveland Cavaliers in 2014 (Keith Allison via Wikimedia Commons)