[Friday: 6.2 miles; Today: 4.4 miles]
When we were building the Classic Book Radio station I did some research on literacy in Lowndes County, MS.
I found some county-level estimates of basic prose literacy at the National Center for Education Statistics. This page talks about how they actual survey data from 1992 and 2003 to create county estimates.
For Lownes it was estimated (at the time I was doing this research) that between 7.7 and 27.1 percent of the adult population did not have basic prose literacy skills. Their website goes into more detail about how they define basic prose literacy skils (BPLS).
You’ll first notice that 27.1 is a pretty high number. And you may notice that the estimate range is wide, nearly 20%. So the actually number of people could be 3,000 or it could be 11,000 or any number in between.
The part I found most interesting was deeper down in the details. How do they do these estimates? They have actual surveys of representative populations from 1992 and 2003 in a few states. They then map those surveys to the demographic data of the county they are estimating based on a set of predictors (quoting from the linked document):
Predictor variables
A key aspect of the small area estimation modeling for the 2003 NAAL and 1992 NALS was finding auxiliary variables that are measured consistently across all U.S. counties and that are effective predictors of the county percentages of adults lacking BPLS. The process of model development involved the compilation of a large number of auxiliary variables that were known or hypothesized to be correlated with literacy. The final set of predictors was selected based on its ability to best account for the between-county variation in the direct estimates of the percentage lacking BPLS for sampled counties.
The best set of predictors for the 2003 NAAL model comprised the following six variables:
- Percentage of the county population who were foreign-born and who had stayed in the United States for 20 years or less years;
- Percentage of county population age 25 and older with only a high school education or less;
- Percentage of the county population who were Black or Hispanic;
- Percentage of the county population in households with incomes below 150 percent of poverty level;
- Indicator variable identifying the New England and North Central census divisions; and
- Indicator variable identifying the SAAL states.
So in the end their map of literacy by county is really a map of education level, poverty, national origin and racial demographics.