2015 report
The studies mention that from 2013 to 2014, there were 15 to 21 million vapers in the United States.
An impressive
estimate of 400,000 ex-smokers out of France alone, now strictly
vape, or have successfully been able to quit both.
You will not find many Solid Statistics on total Vapers worldwide. In Many countries it is Taboo/illegal and people must use extreme caution not to be caught.
In other countries they are more interested in showing wild increase figures for Teen usage or Calls to poison control centers.

The only figures these countries care about are the ones they can use against
vaping.