How widespread are nootropics?

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I have recently become aware of nootropics (here) and instantly loved the idea. Now I am reading everything I can get my hands on.

So I came across this infographic (below) which states that 10% of students used nootropics in 2009 (I presume the data is for USA but I am not sure). In 2016 supposedly around 25% of students are using them.

Can anyone confirm if this data is correct or if there are any up to date statistical studies available?

I know that in my "circle" nootropics are not so widespread - not by far - but than again I have only a small sample size.