What hobbits are going to experience a demographic crunch?
Likely the Stoors. They’re the ones who are closest to humans and occupy the same eco-niches, so most likely to be assimilated.
Harfoots are better at keeping out of the way of humans, and the Fallohides have long displayed better leadership skills to keep hobbits comfortable in their Shire, even if they do occasionally produce a fool of a Took.