Hey...I think you've gotten SOME true information here, and at the same time, I think there have been some comments that are pretty far-fetched. Yes...carcass data is obtained at or around the yearling age because that's when the information is meaningful. We market cattle around 13-14 months of age, so...
Also true, this information is not real helpful without a contemporary group to compare to. And 100 other Shorthorn bulls born the same day as yours on 100 other ranches do not make up a contemporary group! Cattle have to be within an age range of each other and born in the same herd, managed the same way until the data is taken, in order to be able to compare them to each other.
I think the folks at IBE are just taking advantage of technology to try and tell the breeders and the buyers as much as they can about the genetics that are being offered. It can be useful to identify outliers, both good and bad, but you really can't compare the data to other cattle in the sale...you can take it for what it's worth.
As far as the ribeye / square inch of body weight, this is true in general as an average for market cattle at market weights. Like somebody mentioned, I'm not sure it applies to a 2,000 lb Shorthorn bull...maybe it does, maybe it doesn't. I would have to agree that there probably is a point where that correlation levels out and maybe isn't really applicable. In general, the marbling score of 5 sounds relatively high...it would mean a lot more if you had 50 bulls in a contemporary group with scores below a 5, but take it for what it's worth. Especially if there weren't many cattle in the sale that were higher than that. Again...not direct contemporaries so you can't draw too many comparisons. And same thing with the REA, but you really can't compare his 17 inch ribeye to a yearling with a smaller eye and say that's proof that your bull is heavier muscled.
In general, heavier muscled cattle ARE less likely to marble. This is true across breeds as well as within breeds. Look at the difference between Angus and Limousin, for instance... Or any British breed compared to the continentals. And while this is true IN GENERAL, it is NOT the case automatically. There are lots of cattle who disprove that rule, and that's what breeding and selection are all about. It can be done, but it doesn't just happen.