Doug,

If you had been able to attend Tony's clinic Saturday you
would have understood his focus on the percentages of the
national fleet. That isn't a criticism - it's an acknowledgement
of how difficult it is to read and get the same 'feeling' out of
a clinic as you do if you are there in attendance - and I
understand why you weren't there. ;-) The part that is
missing when you read Tony's blog -vs- when you are
there when he is presenting the same topic are the
nuances of expression (the "emphasis").
And, as Tony himself pointed out, the version of his
clinic that was published in MRH does not include -all-
of the charts he presented at BAPM. Those extra charts
showed how he arrived at the final ones for his analysis of
the national freight car fleet - what he did to make better
sense out of the raw data.
An example will explain this better than just words ... one
of the things that Tony did was to eliminate hoppers being
used in mineral service because they skew the numbers.
(Yes, grasshopper, if you are modeling a coal road you can
have - actually NEED - a lot of home road coal hoppers.)

What Tony said - and has reaffirmed in posts here since -
is that if your home road has a smaller percentage of the
national freight car fleet ... you can expect that your
home road will have a smaller percentage of home road
cars "on your layout". And, if I'm understanding Tony
correctly, the number of home road to off road cars
will be different (some number more than the national
average) ... but not as significantly different as you
might think by the oft quoted (and usually erroneous)
percentages such as 40% to 60% (which I suspect that I
shouldn't even be citing those numbers here because it
tends to propagate them even though I'm saying you
shouldn't use them).

There is one aspect that I suspect does contribute to
the increases in home road cars - "captive service".
There are several car types which didn't roam much at
all during the STMFC era (and the further back you push
your date the more this is true). For example, any
cars used in mineral service, cars used by a specific
industry (such as cement hoppers).
In addition, there are "rushes" ... both seasonal and
some for a particular 'era' ... for example the building
boom in California during the 50's tended to keep
flat cars (lumber) busy running back and forth between
the PNW and California.

However, as has been pointed out many times - for
box cars especially - you can't go 'wrong' if you simply
use the national percentages of the car fleet (for your
chosen era).
- Jim B.

P.S. Tony - I have tried to represent you faithfully - if I
have missed on anything PLEASE correct me.