This is also a good tactic though!
I wonder if it is (part) of the reason for the stats you've shown too, people know they're often valued based on what they're already earning. There is also the issue that if you weren't happy and/or were looking to leave anyway then there probably aren't going to be substantial changes in most cases.
Just double check your contract as well for any "restrictive covenants" - Working for a direct competitor, is normally covered by some kind of contract wording etc. Depends on the industry etc but worth checking that as well. (saying that restrictive covenants aren't really worth the paper they are written on most of the time - had plenty of threats in this area in the past and all came to nothing)
Yeah, I guess that varies a bit - if they make them too broad or for too long a duration relative to the actual need then they can't necessarily be enforced. I've had 6 month and 12 month non competes, though the'yve also been reduced down to like 3 or 4 months once the employer has had a rethink or (presumably) some lawyers have advised them that if they want them to be enforcible they need to limit them a bit more in scope.
Also, I guess it depends what they're protecting - if you're in say a sales-related role then whether they choose to try and enforce it might depend on how much of a threat you are - are you going to take away a bunch of clients and cause them damage relative to the cost of enforcement etc.. Ditto to IP, have they got it in place for everyone in certain roles but there are some key people who they'd get rather more concerned about than others re: their knowledge of current IP. In the case of some IP, in particular hedge funds, they can go to extreme lengths to protect it involving shady shenanigans with private detectives etc.. (a friend's brother had his house bugged and was followed by a surveillance team for several months).
The other issue is if there is a relationship between your old employer and your new one, if there is a non-poaching clause then it's game over potentially or the new employer has to buy you out of it.