We do not know of a Web page dedicated to this kind of information. Here's what we have found. 1. The distribution of muscle, fat, and bone is dependent on the level of fatness. Thus, a yield grade 1 will have more lean and less fat than a yield grade 5. So, any "average" numbers will be subject to a wide range. The distribution is also influenced by animal age, breed, and gender. 2. Most of the work is reported as retail cuts (which includes some bone-in cuts like T-bone steaks and short ribs), and fat and bone. 3. The American Meat Institute puts out a publication called Meat & Poultry Facts every year. In 2002, the latest year we could find that contains the data, they reported the average steer as yielding 79.5% retail beef, 20.5% fat and bone. Of course, that includes the fat on retail cuts as well as the bones. 4. The Meat We Eat textbook shows three different sources of data indicating 39.0 to 44.4% steak and roast cuts, 25.0 to 26.3% lean trim, and 29.8 to 36.0% fat and bone. Various other publications show percent separable fat ranging from 21.2 to 23.9%, to which one would add kidney fat of 2.3 to 3.4% (Hedrick, 1968, University of Missouri Research Bulletin 928, "Bovine Growth and Composition"). R.L. Hiner and J. Bond (1971, "Growth of muscle and fat in beef steers from 6 to 36 months of age," Journal of Animal Science 32:225) reported 49% separable lean and 33% separable fat for steers 24 months of age (average live weight of 1,170 pounds, carcass weight of 705 pounds) on full feed. (Of course, this would lead to 18% bone). Clearly the data range widely in the literature. It would be difficult to point to a single source of information as being the "best." We may have to be satisfied with a certain level of ambiguity in the data.

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