I made two simplifications in my thinking. First, I assume that the number of Clojure jobs is constant over the average job retention period. Second, I assume that each job change is advertised exactly once, or the OP evaluation ignores redundant advertisements for the same job. If the latter assumption were not true, the number of actual jobs would be smaller by the redundancy factor. There are studies on the job retention period (e.g. https://hackerlife.co/blog/san-francisco-large-corporation-e...) from which I just took the longest one for a conservative estimate.

The number of responses to the Clojure survey is barely representative for the size of the job market; otherwise you would have to expect millions of respondents for e.g. the JavaScript survey; people responding to such surveys are likely fans of the technology, not necessarily professionals who were hired to use the technology; of course there are also professionals among the respondents, but we don't know the exact proportion.