Pricing up a mock menu in my job interview.
There's not an easy answer to this one Summer.
By GPD I assume you mean Gross Profit Distribution (or Dispersion)?
I also assume you know that obtaining the menu price is based on calculating the cost of the dish, then figuring up to compensate for expected waste (dropped, returned, comped), then dividing by the reciprocal of your projected gross profit.
(Cost / .95 [5%waste]) /.3 assuming 70% Gross Profit
Alternatively, you can take your menu price (MP) subtract the cost (C) then divide by the menu price (MP) to get the gross profit for the dish
Once you figure that for each menu item, you should rank each menu item by the projected likelihood of purchase. Give a higher rank to the items that sell the most and a lower rank to those that don't sell as often. Typically, you want the items you sell the most to have a higher GP. You can generally have a tighter margin on those that don't sell as much, with everything else somewhere in the middle.
One smart marketing strategy that some people use is to identify one item with a high GP and very strong sales- then lower the menu price to a several points below your optimal GP. You will sell A LOT of this item because of its perceived value to the customer, but it will drive up your menu's overall GP due to strong sales. It's kind of like a "loss leader" but with no loss.
I've found The Book of Yields to be a total waste of money. He calculates every yield as a number of servings, but does not specify the size of those servings in any readily usable form. For example, he gives a number 10 can of beans as 24 servings. What use is that to anyone trying to figure cost if you are using the can of beans in a prepared salad or soup with other ingredients? Now if he said a #10 can of beans is 24 1/2 cup servings, or 12 cups or something like that, it would be useful.
Summer, for plated restaurant waste, or shrink of menu items, it depends on a lot of marginally controllable variables: how well staff is trained, how much food is sent back etc. Info that as an interviewee, you do not have access to. For your use, 2% is a comfortable figure. That's 2 out of every 100 plates. You have more control in that scenario.
It's easier if you are making chicken salad for sale by the pound in a deli, for example. I figure 10% in that case for giving samples, returns and the last unservable bit that goes to a staff meal.