On Wednesday of last week, I published an article on disability statistics in Practical eCommerce magazine. Although there’s nothing particularly wrong with the article, I find myself wanting to publish a follow up article with more detail on the statistics. Statistics are complicated beasts, and I feel that detailed explication of sources and statistical problems is well worth while.
First, sources:
Americans with Disabilities: 2005
The primary source for statistics in the Practical eCommerce article was a report called Americans with Disabilites: 2005, produced by the United States Census Bureau. The data dates to 2005, but the report was released in December of 2008, so it’s not far from the most current information available which is based on truly extensive research.
This report was released from data gathered in the Survey of Income and Program Participation in 2005, updating the information from a 2002 report of the same name. The report is limited to the civilian, non-institutionalized population of the nation, and estimates that the overall percentage of the population demonstrating disabilities would rise to 15.7 percent from 15.1 percent if that population was included, referencing information from the 2006 American Communities Survey.
The American Communities Survey
The ACS is a continuous data collection effort by the U.S. Census Bureau used to produce annual estimates at the national, state and local level on the characteristics of the United States population. In 2005, the ACS collected information from approximately 3 million addresses in the United States and 36,000 addresses in Puerto Rico. In 2006, it will also include 2.5 percent of the population living in group quarters, (U.S. Census Bureau, 2003).
Given the rapid pace of technological development, access to ongoing current statistics is of inordinate value to internet-based businesses, although the data is not currently detailed enough to be fully appreciable in web accessibility.
There is a more recent report, from the 2006 American Communities Survey, but the data collection is organized differently, so I elected not to mix the two to avoid introducing errors caused by relating data sets which are not a definite match. Regardless, both sets of data include valuable information, and are well worth consulting.
The primary flaw in this period of American Communities Survey data is that it does not break out separate types of sensory disabilities; blindness and deafness are collapsed into a single category. Although both of these issues have a bearing on web accessibility, the response to the issues is so radically different that this is a major flaw in the data when it comes to web accessibility analysis.
More recent American Communities Surveys have broken this information down further. As of the 2008 questionnaire (downloadable from the Census website), sensory disabilities are separated between blindness/low vision and deaf/hard of hearing.
Cornell University: Disability Statistics
A third fabulous source for disability statistics (with easily the best interface of the group) is the Disability Statistics project at Cornell University. The data is sourced from the American Communities Surveys and the 2000 United States Census, along with a few additional sources, so the base data is the same, but a greater variety of perspectives are available.
The Cornell database requires an account to access statistics, but they do provide free access using a public “guest” account. The email and password entered for the guest account are both “guest.”
Issues with the Data
It was necessary, of course, to summarize the data used for the report. However, each of those numbers should be viewed in context, as well. All of the data referenced is accessible as a Excel download from the U.S. Census Bureau (linked above).
The data is excellent for gaining an overview of the disabled population of the United States, but is not specific enough to give a clear sense of whether these disabilities will impact your web site. The statistics from the American with Disabilities report clearly state, for example, that 3.4% of individuals over 15 years of age have difficulty seeing; a total nearing 8 million people. However, exactly what is included in the data is hard to specify. The information was gathered by asking a series of questions, gathering whether the person had difficulty reading newsprint, etc. It doesn’t specify anything about the nature of the problem.
In general, my assumption is that the data may include some individuals who struggle with reading due to dyslexia, dependent on the exact phrasing of the questions, but not all, and presumably includes no or very few individuals with color blindness.