Codes and Frequencies
For sample adults who used sunscreen at least rarely when they went outside on a sunny day for more than one hour (SUN1SNS), SPFNUM reports the SPF (sun protection factor) number of the sunscreen used most often.
According to the 2000 Field Representative's Manual, if the respondent used more than one kind, the interviewer was directed to probe with, "Give me the number of the sunscreen you use most often or use the most." From 2003 forward, the survey form directs the interviewer to read a similar statement to the respondent if necessary.
Although listed as an acceptable choice for all years, from 2005 forward, the survey form also directs the interviewer to, "Enter '96' if unable to pick the one used most often." In 2010 and 2015, the survey form directs interviewers to, "Enter '50' if 50 or higher SPF."
While the range for SPF levels in SPFNUM runs from 1 to 50, the frequency distribution shows clustering at a small subset of values. By far the largest number of respondents reported an SPF of 15 or 30. For the rest, results cluster at 4, 8, and, for values over 15, multiples of 5.
The Manuals also defined "SPF." The definition in the 2003 Field Representative's Manual was as follows:
The 2000 Manual and the Manuals from 2005 and forward agreed that "[h]igher numbers indicate more protection," but added that, "after a certain point (SPF 15), the extra amount of protection afforded by a higher number is not substantial."
For more information, please see SUN1HR.
While the universe, response categories, and basic question wording for SPFNUM are consistent over time, the optional, supplemental question text for this variable changes over time.
The 2000 questionnaire showed only the basic question, "What is the SPF number you use most often?" However, the 2000 Field Representative's Manual provided additional instructions. If respondents indicated that they use more than one kind of sunscreen or used them for different amounts of time, interviewers were to say, "Give me the number of the sunscreen you use most often or use the most."
These instructions and further instructions on the use of choice '96,' were placed in the survey form in subsequent surveys. Since the interviewer instructions did not change, but rather the placement of the instructions in either the Field Representative's Manual or the survey form, this variable is generally comparable across survey years.
- 2000; 2003; 2005; 2008; 2010; 2015: Sample adults age 18+ who use sunscreen at least rarely.
- 2000, 2003, 2005, 2008, 2010, 2015
- 2000, 2003, 2005, 2008, 2010, 2015 : SAMPWEIGHT