Weighing in on pulled pork.... raw unpulled pork butt (shoulder) yields around 50-60% cooked meat. So to calculate how much raw meat to cook for a large group of guests, first divide the desired portion (say 6 ounces per person) by the decimal percentage of your yield. In other words, divide the 6 by 0.5 or 0.6 in order to determine how much raw meat per serving you will need to cook.
Example. Say that you have 150 guests (or want 150 servings). If we go conservative and figure on a 50% yield after cooking, and 6 ounces per serving, then divide the number of ounces by 0.5 which means that you need to cook 12 raw ounces per serving. (6 divided by 0.5 = 12)
If you feel that you can salvage 60% of your meat, then divide the ounces per serving by 0.6 which comes out to 10 ounces of raw meat (6 divided by 0.6 = 10).
Now multiply the total number of servings by (10 or 12 ounces). 150 x 10 ounces = 1500 ounces. Since there are 16 ounces per pound, you would need 1500 divided by 16, which comes out to 93.75 pounds of raw meat (assuming a 60% yield).
If you are conservative and figure on only a 50% yield, then 150 x 12 ounces = 1800. 1800 divided by 16 ounces comes out to 112.5 pounds of raw meat.
Summary: ounces per serving divided by 0.5 or 0.6 gives us the raw ounces per serving. Raw ounces per serving times the number of guests gives us the total raw ounces, which is divided by 16 to give us the number of raw pounds of pork shoulder (aka butt) to cook up.