I think it's much less likely than inversely proportional, i.e. nonlinear power function.
The probability of the secret remaining secret is the product of the probabilities of all the people involved keeping it secret.
So if each person has a 95% probability of keeping the secret, the probability that no one out of N people divulges the secret is .95^N.
95%^14 < 49%
95%^50 < 8%
95%^100 < 1%