Citation and Abstract

Regional variations in average distance to public libraries in the United States
F. Donnelly
Library & Information Science Research
Volume 37, Issue 4, October 2015, Pages 280–289
http://dx.doi.org/10.1016/j.lisr.2015.11.008

Abstract

“There are substantive regional variations in public library accessibility in the United States, which is a concern considering the civic and educational roles that libraries play in communities. Average population-weighted distances and the total population living within one mile segments of the nearest public library were calculated at a regional level for metropolitan and non-metropolitan areas, and at a state level. The findings demonstrate significant regional variations in accessibility that have been persistent over time and cannot be explained by simple population distribution measures alone. Distances to the nearest public library are higher in the South compared to other regions, with statistically significant clusters of states with lower accessibility than average. The national average population-weighted distance to the nearest public library is 2.1 miles. While this supports the use of a two-mile buffer employed in many LIS studies to measure library service areas, the degree of variation that exists between regions and states suggests that local measures should be applied to local areas.”

Purpose

I’m not going to repeat all the findings, but will provide some context.

As a follow-up to my earlier work, I was interested in trying an alternate approach for measuring public library spatial equity. I previously used the standard container approach – draw a buffer at some fixed distance around a library and count whether people are in or out, and as an approximation for individuals I used population centroids for census tracts. In my second approach, I used straight-line distance measurements from census block groups (smaller than tracts) to the nearest public library so I could compare average distances for regions and states; I also summed populations for these areas by calculating the percentage of people that lived within one-mile rings of the nearest library. I weighted the distances by population, to account for the fact that census areas vary in population size (tracts and block groups are designed to fall within an ideal population range – for block groups it’s between 600 and 3000 people).

Despite the difference in approach, the outcome was similar. Using the earlier approach (census tract centroids that fell within a library buffer that varied from 1 to 3 miles based on urban or rural setting), two-thirds of Americans fell within a “library service area”, which means that they lived within a reasonable distance to a library based on standard practices in LIS research. Using the latest approach (using block group centroids and measuring the distance to the nearest library) two-thirds of Americans lived within two miles of a public library – the average population weighted distance was 2.1 miles. Both studies illustrate that there is a great deal of variation by geographic region – people in the South consistently lived further away from public libraries compared to the national average, while people in the Northeast lived closer. Spatial Autocorrelation (LISA) revealed a cluster of states in the South with high distances and a cluster in the Northeast with low distances.

The idea in doing this research was not to model actual travel behavior to measure accessibility. People in rural areas may be accustomed to traveling greater distances, public transportation can be a factor, people may not visit the library that’s close to their home for several reasons, measuring distance along a network is more precise than Euclidean distance, etc. The point is that libraries are a public good that provide tangible benefits to communities. People that live in close proximity to a public library are more likely to reap the benefits that it provides relative to those living further away. Communities that have libraries will benefit more than communities that don’t. The distance measurements serve as a basic metric for evaluating spatial equity. So, if someone lives more than six miles away from a library that does not mean that they don’t have access; it does means they are less likely to utilize it or realize it’s benefits compared to someone who lives a mile or two away.

Data

I used the 2010 Census at the block group level, and obtained the location of public libraries from the 2010 IMLS. I improved the latter by geocoding libraries that did not have address-level coordinates, so that I had street matches for 95% of the 16,720 libraries in the dataset. The tables that I’m providing here were not published in the original article, but were tacked on as supplementary material in appendices. I wanted to share them so others could incorporate them into local studies. In most LIS research the prevailing approach for measuring library service areas is to use a buffer of 1 to 2 miles for all locations. Given the variation between states, if you wanted to use the state-average for library planning in your own state you can consider using these figures.

To provide some context, the image below shows public libraries (red stars) in relation to census block group centroids (white circles) for northern Delaware (primarily suburban) and surrounding areas (mix of suburban and rural). The line drawn between the Swedesboro and Woodstown libraries in New Jersey is 5-miles in length. I used QGIS and Spatialite for most of the work, along with Python for processing the data and Geoda for the spatial autocorrelation.

The three tables I’m posting on the resources page are for states: one counts the 2010 Census population within one to six mile rings of the nearest public library, the second is the percentage of the total state population that falls within that ring, and the third is a summary table that calculates the mean and population-weighted distance to the nearest library by state. One set of tables is formatted text (for printing or just looking up numbers) while the other set are CSV files that you can use in a spreadsheet. I’ve included a metadata record with some methodological info, but you can read the full details in the article.

In the article itself I tabulated and examined data at a broader, regional level (Northeast, Midwest, South, and West), and also broke it down into metropolitan and non-metropolitan areas for the regions. Naturally people that live in non-metropolitan areas lived further away, but the same regional patterns existed: more people in the South in both metro and non-metro areas lived further away compared to their counterparts in other parts of the country. This weekend I stumbled across this article in the Washington Post about troubles in the Deep South, and was struck by how these maps mirrored the low library accessibility maps in my past two articles.

The NYC Department of City Planning has been collating census data and publishing it for the City for quite some time. They’ve created neighborhood tabulation areas (NTAs) by aggregating census tracts, so that they could publish more reliable ACS data for small areas (since the margins of error for census tracts can be quite large) and so that New Yorkers have data for neighborhood-like areas that they would recognize. The City also publishes PUMA-level data that’s associated with the City’s Community Districts, as well as borough and city-level data. All of this information is available in a large series of Excel spreadsheets or PDFs in the form of comparison tables for each dataset.

The Department of Planning also created the NYC Census Factfinder, a web-mapping interface that let’s users explore census tract and NTA level data profiles. You could plug in an address or click on the map and get a 2010 Census profile, or a demographic change profile that showed shifts between the 2000 and 2010 Census.

It was a nice application, but they’ve just made a series of updates that make it infinitely better:

1. They’ve added the American Community Survey data from 2009-2013, and you can view the four demographic profile tables (demographics, social, economic, and housing) for tracts and NTAs.
2. Unlike many other sources, they do publish the margin of error for all of the ACS data, which is immensely important. Estimates that have a high margin of error (as defined by a coefficient of variation) appear in grey instead of solid black. While the actual margins are not shown by default, you can simply click the Show radio button to turn on the Reliability data.
3. Tracts or neighborhoods can be compared to the City as a whole or to an individual borough by selecting the drop down for the column header.
4. This is especially cool – if you’re viewing census tracts you can use the select pointer and hold down the Control key (Command key on a Mac) to select multiple tracts, and then the data tables will aggregate the tract-level data for you (so essentially you can build your own neighborhoods). What’s noteworthy here is that it also calculates the new margins of error for all of the derived estimates, AND it even calculates new medians and averages with margins of error! This is something that I’ve never seen in any other application.
5. In addition to searching for locations by address, you can hit the search type drop down and you have a number of additional options like Intersection, Place of Interest, and even Subway Stations.

There are a few quirks:

1. I had trouble viewing the map in Firefox – this isn’t a consistent problem but something I noticed today when I went exploring. Hopefully something temporary that will be corrected. Had no problems in IE.
2. If you want to click to select an area on the map, you have to hit the select button first (the arrow beside the zoom slider and print button) and then click on your area to select it. Just clicking on the map without hitting select first won’t do much – it will just highlight the area and tell you it’s name. Clicking the arrow button turns it blue and allows you to select features, clicking it again turns it white and lets you identify features and pan around the map.



3. The one bummer is that there isn’t a way to download any of the profiles – particularly the ones you custom design by selecting tracts. Hitting the Get Data button takes you out of the Factfinder and back to the page with all of the pre-compiled comparison tables. You can print the table out to a PDF for presentation purposes, but if you want a data-friendly format you’ll have to highlight and select the table on the page, copy, and paste into a spreadsheet.

These are just small quibbles that I’m sure will eventually be addressed. As is stands, with the addition of the ACS and the new features they’ve added, I’ll definitely be integrating the NYC Census Factfinder into my presentations and will be revising my NYC Neighborhood Census data handout to add it as a source. It’s unique among resources in that it provides NTA-level data in addition to tract data, has 2000 and 2010 historical change and the latest 5-year ACS (with margins of error) in one application, and allows you to build your own neighborhoods to aggregate tract data WITH new margins of error for all derived estimates. It’s well-suited for users who want basic Census demographic profiles for neighborhood-like areas in NYC.

• The Social Explorer: this web-mapping resource for depicting and accessing US Census data from 1790 to present (including the 2010 Census and the latest American Community Survey data) is intuitive and user-friendly. Many academic and public libraries subscribe to the premium edition that provides full access to all features and datasets (so check with yours to see if you have access), while a basic free version is available online. Given the current circumstances the Social Explorer team has announced that it will open the hatch and provide free access to users who request it.
• The NHGIS (National Historic GIS): this project is managed by the Minnesota Population Center and also provides access to all US Census data from 1790 to present. While it’s a little more complex than the Social Exlorer, the NHGIS is the better option for downloading lots of data en-masse, and is the go-to place if you need access to all datasets in their entirety, including all the detail from the American Community Survey (as the Social Explorer does not include margins of error for any of the ACS estimates) or if you need access to other datasets like the County Business Patterns. Lastly – it is the alternative to the TIGER site for GIS users who need shapefiles of census geography. You have to register to use NHGIS, but it’s free. For users who need microdata (decennial census, ACS, Current Population Survey), you can visit a related MPC project to the NHGIS: IPUMS.
• The Missouri Census Data Center (MCDC): I’ve mentioned a number of their tools in the past; they provide easy-to-access profiles from the 2010 Census and American Community Survey, as well as historical trend reports for the ACS. For intermediate users they provide extract applications for the 2010 Census and ACS for creating spreadsheets and SAS files for download, and for advanced users the Dexter tool for downloading data en-masse from 1980 to present. Unlike the other resources no registration or sign-up is required. I also recommend the MCDC’s ACS and 2010 Census profiles to web designers and web mappers; if you’ve created online resources that tapped directly into the American Factfinder via deep links (like I did), you can use the MCDC’s profiles as an alternative. The links to their profiles are persistent and use a logical syntax (as it looks like there’s no end in site to this shutdown I may make the change-over this week). Lastly, the MCDC is a great resource for technical documentation about geography and datasets.
• State and local government: thankfully many state and local governments have taken subsets of census data of interest to people in their areas and have recompiled and republished it on the web. These past few weeks I’ve been constantly sending students to the NYC Department of City Planning’s population resources. Take a look at your state data center’s resources, as well as local county or city planning departments, transportation agencies, or economic development offices to see what they provide.

The Census FTP site at http://www2.census.gov/

This would be the first logical step, but in the end it wasn’t optimal based on my need. When you drill down through Census 2010, Summary File 1, you see a file for every state and a national file. Initially I thought – great! I’ll just grab the national file. But the national file does NOT contain the small census statistical areas – no tracts, block groups, or blocks. If you want those small areas you have to download the files for each of the states – 51 downloads. When you download the data you can also download an MS Access database, which is an empty shell with the geography and field headers, and you can import each of the text file data tables (there a lot of them for 2010 SF1) into the db and match them to the headers during import (the instructions that were included for doing this were pretty good). This is great if you need every variable in every table for every geography, but I was only interested in one table for one geography. I could just import the one text file with my table, but then I’d have to do this import process 51 times. The alternative is to use some Python to get that one text file for every state into one big file and then do the import once, but I opted for a different route.

The NHGIS at https://www.nhgis.org/

I always recommend this resource to anyone who’s looking for historical census data or boundary files, but it’s also good if you want current data for these small areas. I was able to use their query window to widdle down the selection by dataset (2010 SF1), geography (block groups), and topic (Hispanic origin and race in my case), then I was able to choose the table I needed. On the last screen before download I was able to check a box to include all 50 states plus DC and PR in one file. I had to wait a couple minutes for the request to process, then downloaded the file as a CSV and loaded it into my database. This was the best solution for my circumstances by far – one table for all block groups in the country. If you had to download a lot (or all) of the tables or variables for every block group or block it may take quite awhile, and plugging through all of those menus to select everything would be tedious – if that’s your situation it may be easier to grab everything using the Census FTP.

UExplore / Dexter at http://mcdc.missouri.edu/applications/uexplore.shtml

The Missouri Census Data Center’s UExplore / Dexter tool lets you choose a dataset and takes you to a window that resembles a file system, with a ton of files in it. The MCDC takes their extracts directly from the Census, so they’re structured in a similar way to the FTP site as state-based files. They begin with the state prefix and have a name that indicates geography – there are files for block groups, blocks, and one for everything else. There are national files (which don’t contain small census areas) that begin with ‘us’. The difference here is – when you click on a file, it launches a query window that let’s you customize the extract. The interface may look daunting at first, but it’s worth exploring (and there’s a tutorial to help guide you). You can choose from several output formats, specific variables or tables (if you don’t want them all), and there are a bunch of handy options that you can specify like aggregation or percent totals. In addition to the complete datasets, they’ve also created ‘Standard Extracts’ that have the most common variables, if you want just a core subset. While the NHGIS was the best choice for my specific need, the customization abilities in Dexter may fit your needs – and the state-level block group and block data is conveniently broken out from the other files.

Lastly…

There are a few others tools – I’ll give an honorable mention to the Summary File Retrieval tool, which is an Excel plugin that lets you tap directly into the American Community Survey from a spreadsheet. So if you wanted tracts or block groups for a wide area for but a small number of variables (I think 20 is the limit) that could be a winner, provided you’re using Excel 2007 or later and are just looking at the ACS. No dice in my case, as I needed Decennial Census data and use OpenOffice at home.

Second, for people who are already familiar with GIS and who have various projects to work on (like me) this saves a lot of duplicated effort, as the db provides a foundation to build on and saves the trouble of starting from scratch each time.

Third, it gave me something new to learn and will allow me to build a second part to my open source GIS workshops. I finally sat down and hammered away with Spatialite (went through the Spatialite Cookbook from start to finish) and learned spatial SQL, so I could offer a resource that’s open source and will compliment my QGIS workshop. I was familiar with the Access personal geodatabases in ArcGIS, but for the most part these serve as simple containers. With the ability to run all the spatial SQL operations, Spatialite expands QGIS functionality, which was something I was really looking for.

My original hope was to create a server-based PostGIS database, but at this point I’m not set up to do that on my campus. I figured Spatialite was a good alternative – the basic operations and spatial SQL commands are relatively the same, and I figured I could eventually scale up to PostGIS when the time comes.

I also created an identical, MS Access version of the database for ArcGIS users. Once I got my features in Spatialite I exported them all out as shapefiles and imported them all via ArcCatalog – not too arduous as I don’t have a ton of features. I used the SQLite ODBC driver to import all of my data tables from SQLite into Access – that went flawlessly and was a real time saver; it just took a little bit of time to figure out how to set up (but this blog post helped).

The databases are focused on NYC features and resources, since that’s what my user base is primarily interested in. I purposefully used the Census TIGER files as the base, so that if people wanted to expand the features to the broader region they easily could. I spent a good deal of time creating generalized layers, so that users would have the primary water / coastline and large parks and wildlife areas as reference features for thematic maps, without having every single pond and patch of grass to clutter things up. I took several features (schools, subway stations, etc) from the City and the MTA that were stored in tables and converted them to point features so they’re readily useable.

Given that focus, it’s primarily of interest to NYC folks, but I figured it may be useful for others who wish to experiment with Spatialite. I assumed that most people who would be interested in the database would not be familiar with this format, so I wrote a tutorial that covers the database and it’s features, how to add and map data in QGIS, how to work with the data and do SQL / spatial SQL in the Spatialite GUI, and how to map data in ArcGIS using the Access Geodb. It’s Creative Commons, Attribution, Non-Commercial, Share-alike, so feel free to give it a try.

I spent a good amount of time building a process rather than just a product, so I’ll be able to update the db twice a year, as city features (schools, libraries, hospitals, transit) change and new census data (American Community Survey, ZIP Business Patterns) is released. Many of the Census features, as well as the 2010 Census data, will be static until 2020.

• Since I frequently receive questions about how to use the American Factfinder, I’ve created a brief tutorial with screenshots demonstrating a few ways to navigate it. I illustrate how to download a profile for a single census tract from the American Community Survey, and how to download a table for all ZIP Code Tabulation Areas (ZCTAs) in a county using the 2010 Census.
• New boundaries for PUMAs based on 2010 census geography have been released; they’re not available from the TIGER web-based interface yet but you get can state-based files from the FTP site. I’ve downloaded the boundaries for New York and there are small changes here and there from the 2000 Census boundaries; not surprising as PUMAs are built from tracts and tract boundaries have changed. One big bonus is that PUMAs now have names associated with them, based on local government suggestions. In NY State they either take the name of counties with some directional element (east, central, south, etc), or the name of MCDs that are contained within them. In NYC they’ve been given the names of community districts.
• I’ve done some digging through the FAQs at https://askacs.census.gov/ and discovered that the census is going to stick with the old 2000 PUMA boundaries for the next release of the American Community Survey – the 2011 ACS will be released at the end of this year. 2010 PUMAs won’t be used until the 2012 ACS, to be released at the end of 2013.
• Urban Areas are the other holdovers in the ACS that use 2000 vintage boundaries. The ACS will also transition to the 2010 boundaries for urban areas in the 2012 ACS.
• In the course of my digging I discovered that the census will begin including ZCTA-level data as part of the 5-year ACS estimates, beginning with the 2011 release this year. 2010 ZCTA boundaries are already available, and 2010 Census data has already been released for ZCTAs. The ACS will use the 2010 vintage ZCTAs for each release until they’re redrawn for 2020.

Downloading the data is not as straightforward – the links to extract it just brought me some error messages, so it’s still a work in progress. Until then, a simple copy and paste into your spreadsheet of choice will work fine.

If you like the interface, they’ve created separate ones for downloading profiles from any of the ACS periods or from the 2010 Census. The difference here is that you’re looking at one time frame; not across time periods. The interface and the output are the same, but in these menus you can compare four different geographies at once in one profile. Unlike the Trends reports, both the ACS and 2010 Census profiles have easy, clear cut ways to download the profiles as a PDF or a spreadsheet. If you’re happy with data in a profile format and want an interface that’s a little less confusing to navigate than the American Factfinder, these are all great alternatives (and if you’re building web applications these profiles are MUCH easier to work with – you can easily build permanent links or generate them on the fly).

The US Census Bureau also recently put together a great resource called the Guide to State and Local Census Geography. They provide a census geography overview of each state: 2010 population, land area, bordering states, year of entry into the union, population centroids, and a description of how local government is organized in the state – (i.e. do they have municipal civil divisions or only incorporated cities and unincorporated land, etc). You get counts for every type of geography – how many counties, tracts, ZCTAs, and so on, AND best of all you can download all of this data directly in tab delimited files. Need a list of every county subdivision in a state, with codes, land area, and coordinates? No problem – it’s all there.

In the meantime I have one tidbit I can mention – the Census Bureau has released the 2010 version of the Generalized Cartographic Boundary Files. These files are generalized versions of the TIGER files, with smoothed and simplified boundaries and areas of coastal water removed. They haven’t posted them on the same page as the 2000 and 1990 boundaries; they’ve mentioned they’re creating a new interface to host all of them, which is currently a work in process at http://www.census.gov/geo/www/cob/.

However, you can get access to all the 2010 boundaries via the FTP site – you just need to know what you’re looking at. All the files are named with codes to identify the geographic coverage, summary level, and resolution / scale. There’s a README file on the FTP page that tells you how to identify each.

But in brief – The file names look like this: gz_2010_ss_lll_vv_rr.zip, where:

• ss is the state INCITS / FIPS code which you can look up here – ‘us’ is a national level file.
• lll is the summary level or unit of geography – the README file has a table with each code. The most common ones: 040 for state, 050 for county, 060 for county subdivisions, 140 for census tracts, 160 for places, 310 for metropolitan and micropolitan statistical areas, 860 for ZCTAs. (No PUMAs- 2010 PUMA boundaries haven’t been drawn yet, and 2000 PUMA boundaries are still being used in the latest ACS).
• vv is a version number for the file.
• rr is resolution – most of the files are 500k = 1:500,000, which is the least generalized and best for mapping state-level to regional areas. For national level files you also have the option of 5m = 1:5,000,000 and 20m = 1:20,000,000, which are more generalized and better for national mapping.

The Census Bureau has been doing a lot of tweaking to their website lately. The legacy version of the American Factfinder is set to disappear for good on Jan 20, 2012.

There were two new obstacles I had to contend with this time. The first was that my department has finally migrated to Windows 7 from Windows XP, and I upgraded from ArcGIS 9.3 to 10. I had to reinstall the Export to KML plugin (version 2.5.5) and ran into trouble; fortunately all the work-arounds were included in the plugin’s documentation. I don’t have administrator rights on my machine, so I had to have someone install the plugin as an administrator; this included running the initial setup file AND running Arc as an administrator as you add and turn the plugin on. That was straightforward, but when I ran it the first time I got an error message – there’s a particular Windows dll or ocx file that the plugin needs and it was missing (presumably something that was included in XP but not in 7). I downloaded the necessary file, and with administrator rights moved it into the system32 folder and registered the file via the command line. After that I was good to go.

The second issue was with the Census Bureau’s new American Factfinder. With the old Factfinder the urls that were generated as you built and accessed tables were static and you could simply save and bookmark them. Not the case in the new Factfinder; you can bookmark some basic tables but most of them are “too complex to bookmark”; you can save and download queries from the online ap but that’s it. After some digging I found a CB document that tells you how you can create deep links to any query you run and table you create. The url consists of a fixed series of codes that identify the dataset, year, table, and geography. So this link:

http://factfinder2.census.gov/bkmk/table/1.0/en/DEC/10_DP/DPDP1/8600000US10010

Tells us that were getting a table from version 1.0 of the American Factfinder in English. It’s from the Decennial Census, 2010 Demographic Profiles, Demographic Profile Table 1, for ZCTA 10010 (860 is the summary level code that indicates we’re looking at ZCTAs). So for the plugin to create the links, I just included this URL but for the last five digits I specified the attribute from the ZCTA shapefile that held the ZCTA code. So when the plugin creates the KML, each KML feature has a link generated that is specific to it:

http://factfinder2.census.gov/bkmk/table/1.0/en/DEC/10_DP/DPDP1/8600000US[ZCTA5CE10]

You can see this previous post for details on how the Export to KML plugin works.

For now, the 2010 and 2000 Census are in the new American Factfinder. The American Community Survey, the Economic Census, population estimates, and a few other datasets are still in the older, legacy Factfinder. According to the CB all of this data will be migrated to the new Factfinder by the end of 2011 and the legacy version will disappear. At that point I’ll have to update my PUMA map so that it points to the profiles in the new Factfinder.

You can take a look at the ZCTA map and profiles below (I’m hosting it on the NYC data resource guide I’ve created for my college). As I’ve written before, ZCTAs are odd Census geographies since they are approximations of residential USPS ZIP Codes created by aggregating census blocks based on addresses; you can see in many instances where boundaries have a blocky teeth-like appearance instead of straight lines. Since they’re created directly by aggregating blocks, ZCTAs don’t correspond or mesh with other census boundaries like tracts or PUMAs, or even legal boundaries like counties. In some cases my assignment of county-based colors doesn’t ring true. For example, ZCTA 11370 includes part of the East Elmhurst neighborhood in Queens and Rikers Island, which is in the Bronx. ZCTA 10463 includes the Bronx neighborhoods of Kingsbridge and Spuyten Duyvil and the Manhattan neighborhood of Marble Hill (a geographic anomaly; it’s not on the Island of Manhattan but it’s part of Manhattan borough).

The most salient issue with ZCTAs is that they are only tabulated for the decennial census and not the American Community Survey; the currency of data and spectrum of census variables will be limited compared to other types of geography. ***NOTE*** This is no longer the case – ZCTA-level data is now available as part of the 5-year ACS, beginning with the 2007-2011 series.

View Larger Map

This data is based on the 100% count of the population and is being released for geographies that nest within states: states, counties, county subdivisions, places, census tracts, ZCTAs, and congressional districts, and in some cases block groups and blocks. You can download the data table by table by building queries via the new American Factfinder, or power users can download entire datasets via the FTP site.

You’ll see how small the 2010 Census is compared to the past: we’re only going to get basic demographic variables. The extensive number of socio-economic indicators – education, income, language, employment status, etc – are no longer collected as part of the decennial census; you have to turn to the American Community Survey for this data, which is released on an annual basis.

Here’s what’s in the 2010 Census:

• Total Population
• Urban and Rural Population
• Gender and Age
• Race
• Hispanic or Latino Origin
• Households (Including Type and Size)
• Group Quarters
• Families
• Family Relationships
• Housing Units
• Occupancy Status (Occupied or Vacant)
• Tenure (Owner or Renter Occupied)

Many of these variables are cross-tabulated by age, gender, race, Hispanic or Latino Origin, Household Type, and Household Size. Once we get to the fall of 2011 we’ll start to see national level data for divsions, regions, and metropolitan areas.