Wikipedia is, in general, a very accurate source. It is essentially the collection of current human knowledge and is as credible as you can get when it comes to information. Of course it has its outliers with certain topics, but the site is far from conjecture.
Just so it's clear about this specific thread. This is an article, not a study.
I don't doubt there is validity in those numbers but it's common scientific practice to disclose methods for acquiring the data as well as giving, at minimum, error bars.