Washdown bowls developed from earlier "hopper" closets, which were simple conical bowls connected to a drain. However, waste is typically excreted towards the back of the toilet, rather than the exact center, and the backs of the hoppers were prone to becoming soiled. The modern washdown bowl has a steeply sloping back and a more gently sloping or curving front, so the water trap is off-center, towards the rear of the toilet. With this "eccentric cone" design, most waste drops into the pool of water at the base of the bowl, rather than onto the surface of the toilet. Early washdown closets had a large water area at the base to minimize soiling, which required a large volume of water to clear them effectively. Modern bowls have a smaller area, which reduces the volume of water needed to flush them; however, that water area is always small compared to the water area of a typical North American siphonic bowl, and this makes the washdown bowl prone to soiling.