The average sheep yields about 10 lbs. of wool each year. Once cleaned and carded, that amounts to around 5 lbs. of usable wool. This means that for a duvet containing around 5 lbs. of sheep's wool, you'll need one sheep's worth of labor for a year. From an animal cruelty perspective, a wool comforter or duvet is far better than one made with down. After all, sheep benefit from being safely sheared (usually twice a year) to keep them healthy and happy. In contrast, the geese and ducks used for down tend to have miserable lives that are cut short in a horrific way. And it can take around 40-70 birds to produce enough down or feathers for a duvet.