I couldn't put a percentage on it. Up till fairly recently, I've always just thought of it as something that is there in greater and lesser degrees, greater degrees being more obvious to me in depression. And beyond obvious in panic attacks. Welllll, turns out it's so constant and pervasive that I'm often not even consciously aware of it. It's like living near railroad tracks. What is actually brain-rattling noise, you become oblivious to because it's constantly there.

I loop. And loop and loop. No potential outcome is too unlikely to include. No matter how ridiculous. Straight up situational stuff is another category, but that comes and goes. The loop never stops (and it isn't distinct to a current situation). It can be immobilizing and make decisions nearly impossible. When it gets overloaded, I implode. So, if you were to suggest to either my psych or my BF that I'm anything less than a ball of anxiety, this would be the reaction: Ah, the psych, she has her ways. Poor BF …. see, at home, I talk to myself. A LOT. And it's pretty obvious then…(especially when you realize that muttered loop has reached its 6,500th rotation…. )
(And yes, I do have (um, apparently 2) anxiety dx separate from my BP dx.)

In terms of how much it bothers me in the scheme of things? Outside of near-blackout sheer panic, not as much as you might think given how constant it is. Remember the railroad.
Anxiety, in general, I can deal with better than the straight up BP stuff like:
agitation
frustration
lack of control
cognitive problems

Those bother me FAR more. As in being distressing to downright mortifying.