Mine is easily less than half the national average. It's not hard when you don't fly for work or pleasure and you don't drive a car but car pool, bike or bus instead. Simple little things make a big difference at year end as well, composting, shopping at the thrift store, gardening and/or sprouting, collecting rain water, shutting off lights and unplugging appliances after use, supporting local producers, and biggest and best of all ~ remembering the most important of the three R's, reduce and reuse. Recycle is the Last and least effective on that particular list.
I'm thinking about a composting toilet next, all my research tells me it's way better than it sounds.
Walk lightly on the face of the Mother and she will reward you a thousand fold.