Beef Shoulder Clod Ground Beef: What's the % Lean?

Once upon a time, I bought a beef shoulder clod, and instructed the butcher on what I wanted from it. Along with all the steaks and roast portions, came the balance as ground beef. Well after the fact, I wanted to know: What is the lean / fat ratio of the clod ground beef? So, I asked my Facebook community how to find out.

The suggestion I took was to compare the before and after cooking weights as an approximation. I did that, got (after / before) = .70, so (before / after) = 1.43

Another Facebook friend asked that I perform the same experiment, but specifically with Wegmans 90% / 10% ground beef. He offered to buy the beef, and I agreed to do the work. I did that, got (after / before) = .80, so (before / after) = 1.25

Omitting the long story here, I got to a website that has a database full of nutritional values. Of interest, there are USDA values for ground beef, both 75% / 25%, and 90% / 10%. Best of all, there are USDA values (grams protein and grams fat) for 1 ounce of both, raw and broiled. Now we're cookin' ...

75%
raw: protein 4.6 g fat 7.1 g
broiled: protein 7.2 g fat 5.3 g

90%
raw: protein 5.7 g fat 2.8 g
broiled: protein 7.4 g fat 3.3 g

Make the simplifying assumption that air frying and broiling are very similar cooking processes. Make the simplifying assumption that adding heat to meat does not increase or decrease protein. We can now presume, indeed observe, that 1 ounce of broiled beef started from more than 1 ounce of raw beef. So, let's calculate those ratios:

USDA 75% (broiled to raw) 7.2 / 4.6 = 1.565
USDA 90% (broiled to raw) 7.4 / 5.7 = 1.298

In words, if I want the protein of 1 ounce of cooked 75% lean ground beef, I need to start with 1.565 ounces of 75% lean ground beef. Same way, I need to start with 1.298 ounces of 95% ground beef. Those are decent approximations to shrinkage ratios. Let's compare.

Wegmans 90% lean ground beef showed shrinkage of 1.25. Very close to the USDA ratio, indeed, a bit better. All things considered, dead on target.

My shoulder clod ground beef showed shrinkage of 1.43. Using the USDA numbers, and interpolating (an exercise left to the student), my clod ground beef is about 82.5% lean.

I believe 82.5% lean is a much better value than the simple shrink approximation of 70%.