Reliable data is lacking due to a lack of polling and the varying definitions of vegetarianism and veganism used in the polls. For example, the latest US poll defines "vegan" according to diets that exclude meat, eggs and dairy, rather than following the accepted definition of veganism as avoiding all animal products as far as possible including honey and clothing. Other polls, like the latest Australian poll, place strict vegetarians and those who follow "almost" vegetarian diets in the same category, while this poll and many others measure only vegetarianism and neglect to include veganism in the poll. Many poll results are contradicted by other poll results from the same country despite similar publication dates, implying a wide margin of error.
A study from 2010 estimated that there are 1,45 billion vegetarians of necessity and another 75 million of choice. They make approximately 21.8% of the world’s population.