Do the actual search, and look at the results:

http://www.indeed.com/jobs?q=scheme&l=

Not so convincing anymore, right? Obviously, 'scheme' is a generic word, giving many vacancies not related to the programming language Scheme.

There's no good way to easily gauge scheme with this site. At first I typed in "scheme programming language" and came up with 250 results, "scheme lisp" provided something slightly more relevant, but with only 45. I didn't scroll through, but even then they were only asking for people with experience in scheme (among other languages that aren't de jour, like smalltalk).

Sure, at least he showed this percentage on the Y-axis. That still means there are five times as many Scheme jobs than for Scala, Groovy, Clojure, Erlang. That's not the case (although I wish it were), just search for "scheme" on indeed.com.