Via "Create a Trend" option concerning Gallup Poll Social Series: Work and Education surveys. Question 33b (August 2008), Question 27b (August 2006), Question 38b (August 2005), Question 38b (August 2004), Question 30b (August 2003), Question 63b (August 2002) and Question 45b (August 2001). 4 pages., Traces responses of U. S. adults to this question in seven surveys, 2001-2008.