Mike

Ok, you're wearing me down :-) I dismiss the 1938 books as irrelevant,
but if you show a consistency from 1949-1956 then I think it's worth
some digging down and trying to find out WHY SP box cars were so much
more common on the UP than random distribution would predict. First I
would seek to know what percent of the SP cars were loaded, and what
percents loaded EB/WB. Answers to those might lead further inquiries
in a useful direction...

Tim O'Connor