A postcard was first mailed for notification of the
forthcoming survey. The paper questionnaire was then
mailed 1 week later, with a description of options to
complete the survey online or to return it by mail.
Reminder postcards were sent a week later, followed in
1 week by duplicate surveys, mailed only to nonresponders.
Email reminders were sent to non-responders if
the duplicate survey was not returned within 2 weeks. If
mailings were returned undeliverable, attempts were made
to find correct addresses or confirm ineligibility.