The 37% is referencing what's called the Secretary problem on Wikipedia and comes from 1/ℯ:
Although there are many variations, the basic problem can be stated as follows:
There is a single position to fill.
There are n applicants for the position, and the value of n is known.
The applicants, if all seen together, can be ranked from best to worst unambiguously.
The applicants are interviewed sequentially in random order, with each order being equally likely.
Immediately after an interview, the interviewed applicant is either accepted or rejected, and the decision is irrevocable.
The decision to accept or reject an applicant can be based only on the relative ranks of the applicants interviewed so far.
The objective of the general solution is to have the highest probability of selecting the best applicant of the whole group. This is the same as maximizing the expected payoff, with payoff defined to be one for the best applicant and zero otherwise.
A candidate is defined as an applicant who, when interviewed, is better than all the applicants interviewed previously. Skip is used to mean "reject immediately after the interview". Since the objective in the problem is to select the single best applicant, only candidates will be considered for acceptance. The "candidate" in this context corresponds to the concept of record in permutation.
The 37% is referencing what's called the Secretary problem on Wikipedia and comes from 1/ℯ: