Tim has much better luck than I do. I routinely only get 50% of my pre-cooked weight in final pulled pork.
In fact, I just did two boneless Butts this past weekend for a dinner for out of town family. Pre-cooked was a smidge over 16 lbs. Final product was about 7½ lbs.
There were about a dozen diners, some big eaters, some not. We also had BBQ Beans, Mac-n-Cheese, and a Broccoli Salad. We did have leftovers.
BD