About the Authors

Corresponding Author

katherine.ahrens@sfdph.org

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

CKK, JAM, HR, JM, PK, and JDK conceived and designed the experiments. KA, JAM, and HR analyzed the data. KA, CKK, JAM, HR, JM, PK, and JDK wrote the paper. JM worked closely with Better World Advertising in the planning and development of the campaign in 1999.