In my adult life I've had 4 dogs. All big. 2 greyhounds, 1 doberman, 1 great dane. None of them have ever tried to jump a 4' fence.
Yes, some dogs will try and succeed in getting over a 4', or a 5' or even a 6' fence. T and Abby can easily clear our fence if they wanted to. Abby will jump from about 14 feet back and clears the steps to the deck with ease - ground to the deck is 3.5 feet. But she has never tried to go over our fence. Not all dogs, even if they can do the jump, will.