The number of vegans in the UK is estimated at around 180,000 or 0.3% of the population (based on the surveys below, see note).

Year	% of UK population	No of vegans	Source
2007	0.3%	162,000 *	(13)
2006	0.1%	86,000 *	(12)
2005	0.5%	279,000 *	(11)
2004	0.6%	363,000 *	(10)
2003	0.4%	235,000 *	(9)
2002	0.2%	132,000 *	(8)
2002	0.1%	71,000 *	(7)
2001	0.3%	176,000 *	(6)
2001	0.3%	182,000 *	(5)
2000	0.3%	195,000 *	(4)
1997	0.4% *	224,000	(2)
1995	0.3% *	170,000	(2)
1994	0.2%	112,000 *	(3)
1993	0.2% *	100,000	(2)
Avg	0.3%	178,000	(1)

* This number has been extrapolated to enable comparisons between surveys. It is based upon the latest population estimates available and may therefore change over time.

NOTE:
These figures exclude the DEFRA, Public Attitudes and Behaviours toward the Environment 2007 study which erroneously estimated the number of vegans in the UK at over 1.3 million (2.2%). This was due to a proven misclassification between vegans and vegetarians and resulted in a published figure that was incorrect by a factor of ten.

(13) Food Standards Agency, Consumer Attitudes to Food Standards 2007.
(12) Food Standards Agency, Consumer Attitudes to Food Standards 2006.
(11) Food Standards Agency, Consumer Attitudes to Food Standards 2005.
(10) Food Standards Agency, Consumer Attitudes to Food Standards 2004.
(9) Food Standards Agency, Consumer Attitudes to Food Standards 2003.
(8) Food Standards Agency, The National Diet & Nutrition Survey 2002.
(7) Food Standards Agency, Consumer Attitudes to Food Standards 2002.
(6) Food Standards Agency, Consumer Attitudes to Food Standards 2001.
(5) Today/ICM Research Poll - Feb 2001.
(4) Food Standards Agency, Consumer Attitudes to Food Standards Report, Oct-Dec 2000.
(3) MAFF Dietary Survey of Vegetarians 1994-1995 UK Data Archive.
(2) Realeat/Gallup surveys into Meat-Eating and Vegetarianism, from the introduction to The Vegan Shopper, published by The Vegan Society, Jun 2000.
(1) The mean average based on all surveys.

FURTHER INFORMATION:
Vegetarian stats since 2000: www.vegsoc.org/page.aspx?pid=753

The available research puts the figure at around 1% of the USA population.

2008: 0.5% of the population (6)
2006: 1.4% of the population (5)
2003: 1.8% of the population (4)
2000: 0.2% of the population (3)
2000: 0.9% of the population (2)
1997: 1.0% of the population (1)

(6) 2008 Harris Interactive survey, Vegetarian Times.
(5) 2006 Harris Interactive survey, Vegetarian Resource Group.
(4) 2003 Harris Interactive survey, Vegetarian Resource Group.
(3) 2002 CNN poll, Time Magazine.
(2) 2000 National Zogby Poll, Vegetarian Resource Group.
(1) 1997 Roper Poll, Vegetarian Resource Group.

FURTHER INFORMATION:
2005 Teen Poll: www.vrg.org/journal/vj2005issue4/vj2005issue4youth.htm
2000 Teen Poll: www.vrg.org/journal/vj2001jan/2001janteen.htm
1995 Teen Poll: www.vrg.org/journal/95nov.htm#kids
1999 Dining Poll PR: www.vrg.org/press/99novpollrest.htm
1999 Dining Poll: www.vrg.org/journal/vj99sep/999scientific.htm
1994 Adult Poll: www.vrg.org/nutshell/poll.htm

Very little information is available outside the UK/USA.

FURTHER INFORMATION:
www.euroveg.eu/lang/en/info/howmany.php
www.ivu.org/news/95-96/general.html

The following websites/pages include information about veganism and clinical research:

Research on Vegetarians & Vegans
Vegetarian Nutrition
Vegetarian and Vegan Foundation
Vegan Society Nutrition & Health
PCRM Clinical Research
Scientifically-Credible Information on Vegan and Vegetarian Diets