20 -- It's hard to estimate how much food is wasted at the supermarket level, but one estimate puts it at a $20 billions (with a 'b') value per year just for the US. That's 8-10% of total perishable goods in the country (and more is wasted after it is bought).
48 -- That's how many billions (with a 'b' again) the United Nations estimates that US retailers and consumers throw away each year.
1/2 -- European retailers waste half as much food as US retailers. Part of the reason for that is that food has to travel for longer distances in the US.