Using a Russet potato as a replacement for you-know-what, Wilcut flushes the spud down a Caroma toilet with the full flush (1.6 gallon) AND half flush (0.8 gallon) for liquid waste to show how a dual flush system can efficiently dispose of waste. Since toilets make for almost 30% of residential indoor water use in the United States, it seems like a no-brainer in water tight times for new homes to all come with high efficiency toilets, alongside home owners being given an incentive to convert to dual flush models to replace aging and leaking units.
According to the Pottygirl site, the average person flushes the toilet nearly 140,000 times in their lifetime, and by switching over to a water efficient, a person can save up to 4000 gallons of water per year. You can figure out your savings yourself using an online calculation sheet. What you want look for is a WaterSense Labeled High-Efficiency Toilet. More details and resources about this important subject over at Pottygirl.