I'm afraid to ask what the other 20% is. Is that number something about the fat content?
80% meat, 20% fat.
Yes, 20% pure fat.
In most instances it's fat. But you have to be careful because now in some cases they're adding non meat fillers. Look for an ingredients label. There shouldn't be one. It should be 100% beef (or pork).
I came across some fresh Italian sausage the other day that had 'soy grits' in it. Now I have to check labels on an all meats.
They also like to inject water in the form of a broth in many cuts of pork and chicken, sometimes beef. You could be paying for up to 20% water in some cuts.
And don't forget the carbon monoxide packaging to keep the beef bright red indefinitely. If you see the meat wrapped in plastic packaging that's looks inflated like a balloon it's probably been pumped with carbon monoxide.
Watch for more and more adulterated meats as prices continue to climb.