Even if you did, it strikes me that this is an absurd metric. Since a lot of C development goes on within communities; either closed source shops, or open source projects, where it's likely only a portion of the mailing list archives, if any of them at all, are archived. The majority of the BSD and Linux kernels are written in C, along with a significant percentage of the toolsets, so clearly there's one helluva lot of C coding going on. Whether search engines index that activity or not is irrelevant.
A better metric, though not perfect, would be to look at the activity in places like Git, to see how many lines of code roughly are in any given language.