--- In STMFC@..., "Mike Brock" <brockm@...> wrote:

The real UP...as I said...should see...over a long data sample

...one MWR car every ten days. My sample of the real UP box car data
is so small that IF I want the appearances of box cars to match the
long term ratios, I can't include cars with less than one car.

Maybe you COULD include "cars with less than one car" by cycling them
into and out of your mix so that they would only appear rarely, rather
than not at all. Instead of leaving your MWR car on the layout month
in and month out, just put it on the railroad once every ten sessions.
True, it's more work, but it might contribute to the authenticity of
your sessions by having oddball cars show up ONCE in a while.

Walt Lankenau