It's actually very interesting to go on the websites for these companies. Fred is right, they have it down to two decimal places. Not only feed conversion to egg mass, but also size of egg, number of inclusions such as meat spots in the egg, etc. Check this out:
http://www.isapoultry.com/en/products/
I really like my production line poultry. My white Leghorns are great layers and forage very well, also. They are not pet chickens by any means, but they are beautiful and do the job. I also like the commercial Red Sex Links. They lay very well (with the exception that the egg size can get too large if you don't restrict certain nutrients at 80% of desired egg size, but I can't do that and the commercial guys can) and are the calmest, sweetest chickens I own.