Babies are the best pump. They empty the breast better than either hand expression, manual or electric pumps. Even as the most efficient pump, babies never completely empty the breast. Breasts work on what could be called the “80:20 concept.” The 80 percent is the average amount of milk removed by your baby each day. The 20 percent is the residual amount of milk that remains in your breasts. If more than 80 percent of the milk is removed, supply increases to maintain the 80-20 ratio. If less than 80 percent is removed, supply decreases to maintain the 80-20 ratio. Even though this is an over-simplification of a very complex process, as new research emerges this core principle proves true.