First, Natural Calm is sold by weight and not by volume. As with other powdered products, settling occurs. When the powder is bottled, it is extremely fluffy from the production process. There is so much air mixed in with the Calmful Sleep, that the powder must be pressed down manually in order to seal the cap. Over time, the product settles and the volume decreases, but the total amount of product by weight does not change. So, the powder becomes more dense and takes up less space in the bottle.