Table 1. Characteristics of studies included in the review.

ID	Date Country	Sample	Method	N (%)	Self-/Non self-	Quality
Tangney, 1987 [32]	n.s US	Researchers in a “highly ranked American university”.	Distributed within department	245 (22)	n	1
Lock, 1988 [29]	1988 UK	Professors of medicine or surgery, other academics, doctors, research managers, editors of medical journals non-randomly contacted by the author	Mailed+pre-paid return	79 (98.7)	n	0
Simmons, 1991 [54]	1989 US	Active members of the Society of University Surgeons	n.s.	202 (82)	n	0
Kalichman, 1992 [35]	1990 US	Research trainees in the clinical and basic biomedical sciences at the University of California, San Diego	Distributed through the department	549 (27)	s+n	1
Swazey, 1993 [53]	1990 US	Doctoral students and faculty, from 99 of the largest graduate departments in chemistry, civil engineering, microbiology and sociology	Mailed+prepaid return+postcard to confirm response	2620 (65.5)	n	1
Glick, 1993 [55]	1992 US	Biotechnology companies' executives known by the author	Administered orally, on the phone	15* (n.s)	n	0
Greenberg, 1994 [20]	1991 US	Members of the Society for Risk Analysis, Association of Environmental and Resource Economists, American Industrial Hygiene Association	Mailed	478 (32)	n	1
Glick, 1994 [30]	1993 US	Attendees at the Third Conference on Research Policies and Quality Assurance	Handed out, personally returned by respondents on the same	36 (34)	n	1
Eastwood, 1996 [56]	1993 US	All postdoctoral fellows registered with the Office of Research Affairs of the University of California, San Francisco	Mailed+follow-up letter	324 (32.8)	s+n	1
Bebeau, 1996 [33]	1995 US	Program chairs and officers of the American Association for Dental Research	Mailed+prepaid return+postcard to confirm response	76 (78)	n	1
Rankin, 1997 [57]	1995 US	Research coordinators or directors of master's and doctoral nursing programs	Mailed	88 (43)	n	1
May, 1998 [34]	1997 UK	Randomly selected authors of papers published in the past 3 years on addiction-related subjects	Mailed	36 (51)	n	1
Ranstam, 2000 [46]	1998 Various	Members of the International Society of Clinical Biostatistics	Mailed+online electronic version	163 (37)	n	1
List, 2001 [28]	1998 US	Participants to the January 1998 meetings of the American Economic Association	Hand-delivered, Direct Response+Random Response method, drop box for returning responses	94 (23.5)	s	1
Geggie, 2001 [58]	2000 UK	Medical consultants appointed between Jan 1995 and Jan 2000 working in 7 hospital trusts in the Mersey region	Mailed+pre-paid return	194 (63.6)	s+n	1
Meyer, 2004 [59]	n.s US	Members of editorial boards of American Accounting Association journals, and participants at the 1998, 1999, and 2000 American Accounting Association New Faculty Consortia	Email asking to reply if unwilling to participate, mailed+pre-paid return	176 (48.5)	n	1
Martinson, 2005 [19]	2002 US	Researchers funded by the National Institutes of Health	Mailed, pre-paid return, 2$	3247 (47.2)	s	1
Henry, 2005 [60]	2002 Australia	Medical specialists, from the 2002 edition of the Medical directory of Australia, involved in pharmaceutical industry-sponsored research	Mailed	338* (n.a.)	s	1
Gardner, 2005 [27]	2002 Various	Authors of pharmaceutical clinical trials published in the Cochrane Database of Systematic Reviews, equally selected between first, middle and last author.	Mailed+10$ check+second survey to non-respondents+follow-up call or email	322 (64)	s+n	1
Kattenbraker 2007 [61]	2005 US	Health education professors at every rank, teaching at 94 institution of higher education	Email+web-based survey+follow up email+final reminder	153 (25.8)	n	1
Titus, 2008 [31]	2005 US	Researchers funded by the National Institutes of Health, one per department	Pre-notification+mailed+reminder postcard+additional survey packet+follow-up letter	2212 (52)	n	1

Abbreviations: “Date” is the year when the survey was actually conducted, “N” is the number of respondents who returned the questionnaire, “%” is the response rate of the survey.

^*Number of respondents who ad engaged in industry-sponsored research in the previous 12 months, out of a total sample of 2253, with 39% response rate.