Rust, by the way, goes back further than 2012; it became public in 2010.

IRC:

- irc://irc.mozilla.org/#rust: 480 people

- irc://chat.freenode.net/#elixir-lang: 158 people

On GitHub:

- mozilla/rust: 414 watchers, 4,776 stargazers, 993 forks.

- elixir-lang/elixir: 217 watchers, 2,317 stargazers, 323 forks.

Reddit:

- /r/rust: 3,754 rustaceans, ~30 users here now, 172 posts in the last month

- /r/elixir: 448 developers, ~6 users here now, 14 posts in the last month

Mailing lists:

- rust-dev (it hasn't been split yet like elixir's are and is mostly development stuff; /r/rust is used more for other talk): 50 threads this month

- elixir-lang-talk: 45 threads this month

- elixir-lang-core: 23 threads this month

Stack Overflow

- [rust]: 294 questions

- [elixir]: 119 questions

Google Trends: https://www.google.com/trends/explore#q=rust%20programming,e... shows "rust programming" at around 3× "elixir programming"

I agree that elixir is a little closer to being a mature language (for Rust, 1.0 is not expected for some months yet, though probably still this year), and the elixir community does appear to be more active and mature than I had thought, but overall it still looks to me as though Rust has at the very least the larger community (I'll drop the active claim out of laziness and the mature claim for insufficient evidence) by a considerable way.