Here is a common answer from 2016:
Some 542,000 people aged 15 or over – more than one per cent of the population – have adopted a plant-based diet, up from 150,0001 in 2006.
While this is great, it's just a single number showing the increase over one period of time. I want to know how the rate of increase is changing. If it remains at a steady increase of ~40,000 people per year, it will take a long time for veganism to become mainstream. Some indirect measures (e.g. veganuary signups, google searches) indicate that the rate is increasing, but I'm hoping to see direct results from surveys, or something close.
Information about the growth of vegetarianism is also welcome.
Answers can either be restricted to a country or region or be about the world as a whole.
1 This is usually (including in the source) reported as an increase of 360%, which is wrong. 542,000 is 360% of 150,000, but the vegan population increased by 260%.