Since Jerry wanted the reference for 205 day weights, it's Koger and Knox

J. Anim Sci Vol 4:285. As a student at Florida, I heard Dr. Koger expound

on this topic more than once. He was frustrated that people adopted the

205 day standard when his paper recommended adjusting to the mean. If you

look at the paper, you will find a Nomograph that lets "calculate" the 205

day weight with a straight edge connecting the age and weigh axes of the

nomograph and reading the adjusted weight from a regressed line. Given the

alternative of the day of slide rules or pencil and paper, the nomograph

increased efficiency of calculating the adjusted weights by several orders

of magnitude. Of course, if you changed the age of adjustment, you would

need to change the regressed line on the nomograph. So people just use the

one out of Koger and Knox rather than draw their own nomograph. So that's

the history lesson for today.