NEW SKILL: Dodging (P/H), Defaults to (DX + HT)/2
  This skill is based on (DX + HT)/2, rounded *down*. It represents 
training in the skill of dodging attacks. Your actual Dodge score is 
equal to 1/2 of your Dodging skill. Note: The GM may wish to restrict 
this skill, as described under Cinematic Maneuvers in GURPS Martial Arts. 

So now someone who's .5 points away from a higher Dodge score can up his 
Dodge for 8 points. Someone a point away can up it for 16 points. And so 
on. For some reason, I expect to hear an argument about, "But this skill 
is worthless if they just put a few points into it!", to which I'll 
answer now: DUH. It's designed that way, to preserve Game Balance(TM). 
The ability to Dodge is powerful; you can Dodge a billion attacks each 
round! It SHOULD be expensive.