I find this hard to believe, but I am a relative novice.Ok, try this then: I once calculated a correlation of greater than .9
between the number of foreign road boxcars reported in a SRR wheel report
and the percentage of each of those foreign roads contribution of boxcars to
the national fleet. That's a pretty strong relationship.
IIRC the sample was ~800 boxcars in 20-25 trains. Because the wheel report
book travels w/ the conductor, not the station, the elapsed time was a ~5-6
weeks. Had it been a sample from a single location on the same route I
understand it would have taken just a couple of days to see the same number
of boxcars. The trains in the sample were scheduled, extra, second section,
through freight, and local and spanned all hours of the day and all days of
the week. The conductor had almost 20 years of service at the time.