If all your fixtures are equally recent, it's likely that the toilet is the biggest use. But it might also be the most difficult one to reduce. In any case your per-capita consumption is already exemplary. Here in California the most extreme conservation measure they have managed to think up is households using more than 1000 gallons per day will be charged slightly more at the margins. I always look at these conservation proposals, then I look at my own bill, and I figure there's nothing I personally need to do.