How many YC startups use Lisp and is it faster?

I realize lisp is a recurring topic here, but I haven't seen numbers:

1. how many yc startups actually use it? 2. have non-pg people who have really used it really found it to make them measurably faster, and if so, by how much?

PS: clearly "faster" is hard to measure, so to unpeel once:

(a) self vs self on same task (b) team vs itself after language migration