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Codes and Frequencies

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For sample adults aged 18 and over who are not blind or for whom it was unknown if they are blind, VDIFDRIVE rates an individual's difficulty level of driving during daytime in familiar places even when the person wears glasses or contact lenses.
This variable is included in the Sample Adult Vision Supplement, sponsored by the National Eye Institute.


Apart from a slight change in the universe and an introduction of a new category in the response format in the 2002 and 2008-forward surveys, VDIFDRIVE is comparable over time. Please see the Universe tab for changes in universe between samples.
The changes in response categories allow for further detail as to why a person cannot perform an activity. In 1999, the response format was constructed on a five-point, ranging from "not at all difficult" to "can't do at all" (along with unknown responses). In the 2002 survey, a new category "do not do this activity" was added. In 2008, the categories "can't do at all" and "do not do this activity" were reworded to "can't do at all because of eyesight" and "do not do this activity for other reasons."


  • 1999; 2002: Sample adults age 18+ who are not blind or REF/NA/DK if blind or REF/NA/DK if have trouble seeing even when wearing glasses/contact lenses.
  • 2008; 2016 2017: Sample adults 18+ who are not blind or for whom it was unknown whether they were blind.


  • 1999, 2002, 2008, 2016-2017