How can the data be valid? If it's based on the CV profile of each individual then that will be counted is inaccurate, most of them use the keyword "crypto" so all parts will enter. I think this is unfair if it is said to be blockchain development statistics.
That is why I suggested to @phwizard to include some more detail as to the methodology used to derive the data (nº of CVs parsed/non-parsable, keywords, and assuring keywords are used in a developer content as opposed to non-developper).
The stat is likely a decent approximation though, based on referenced keywords (I don't know how job roles are treated), but degrees of real expertise behind each CV is obviously not going to be evaluated. @phwizard has provided additional information on this thread, with a link to some of the underlying aggregate absolute and proportional data: Since he is actively responding to questions here, he will likely get back to you on your concerns.
@phwizard, just to point out that it is common practice to answer multiple posts within a single post (quoting whatever is necessary from each), in order to avoid posting multiple times in a row...