Your sample is heavily skewed toward the literate. Add Education (None,HighS,BS,MS,PhD) as a research statistic and compare it to the national average. I would

Your sample is heavily skewed toward the literate. Add Education (None,HighS,BS,MS,PhD) as a research statistic and compare it to the national average. I would bet that your sample is greater than 2 Standard Deviations from the mean.