Insane difference between 6mm vs 7mm cord

Here is an interesting video on the break strength of accessory cords.  In the world of climbing and guiding sometimes accessory cord comes out as rescue lines used by qualified professionals.  There is a big difference with the jump from 6mm to 7mm cord.  In this video, we get a quick rundown of why this is along with some pretty good visuals on breaking rope. 
Pro tip: Always remember that any knot in a rope will significantly reduce its breaking strength.