Greg wrote in part:
"We have to presume that the IHC was reported into the NYC numbers for revenue purposes, just as the Sacramento Northern was in the WP numbers. For the LA Basin I am not sure who was responsible for the small amount of revenue the LA Junction or the Pacific Harbor Line generated, I would suppose it was split between the parents."
It didn't work quite the way that Greg presumes/supposes. This is the reporting requirement as quoted from the 1952 annual report:
"Under the Commission's order of September 24, 1946, as amended, steam railway companies, other than switching and terminal companies, assigned to Class 1, are required to make quarterly and annual reports of freight traffic statistics, in duplicate, and for that purpose this form is provided."
Here's the 1952 definition of freight traffic originating on respondent's road:
"Originated on respondent's road means: (a) shipments originated directly on respondent's road; (b) shipments received from water lines and highway motor truck lines, except when identified as having previous rail transportation; (c) shipments which received first line haul on respondent's road, but originated on switching lines connected directly or indirectly with respondent's road; (d) import traffic received from water carriers, and traffic from outlying possessions of the United States; (e) outbound freight which has been accorded transit privileges."
The 1952 definition of freight traffic terminating on respondent's road is worded similarly.
So in 1952 the IHB was a Class 1 Switching and Terminal Company (which happened to be in the Chicago Switching District), not a Class 1 steam railway. It was not required to report (under this order), and it's statistics weren't lumped with the NYC (parent company). Suppose we have a load originating on the SP, interchanged to the UP and then the CNW, and finally delivered to a consignee on the IHB. This would have been recorded as a shipment of lumber, shingle, and lath originating on the SP, through for the UP and CNW , and terminating on the CNW (Note the potential for double counting; recognized by the designers of the study).
In most cases, especially within switching districts, the originating line haul carrier (or the terminating line haul carrier) is a Class 1 steam railway and the carload is reported. But there are cases where the originating (or terminating) line haul railway is NOT a Class 1 Steam Railway NOR a switching or terminal line (loads originating and/or terminating on the Atlantic and Danville for example). In such cases the statistics were "missed" by this reporting system. This is one of the two reasons why for a given commodity in any given year the number of originations did not match the number of terminations.