Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

The above data falls short of the quality of the
%information that was available for the grain study. As
government publications go, a seven digit classification
is relatively detailed. It, nevertheless, represents an
aggregation of shippers with different costs of production,
who are located differently and who face different transport
costs. The empirical work had, for example, to proceed as
if all producers were located in the New York customs
district and paid transport from there to Great Britain.
Almost all of the seven digit groups involve more
than one commodity, and some more than a hundred. There
is every reason to believe that the individual commodities
within any group have different values per pound, but
the average of the entire group had to be used. It is
known that several different rates are charged for many
of the individual commodities within a seven digit group.
This cut the potential sample size down as was explained
above. Rate structures are, in addition, tapered. Since
quantities for individual commodities within a group, and
the frequency distribution of sizes of shipments were
unknown, simple average rates were used.
Finally, data on total transport time, as against
schedule time which is considered misleading because of
days in loading, unloading, queuing, etc., were only
available for a single firm which estimated that sea and
air delivery required thirty-eight and nine days respectively.
These times were used in a test run of a subsample of our
459 sample with results that are mentioned below. In
summary, the statistical analysis of competition between
air and sea had to be cross sectional, each seven digit
group being treated as the homogeneous output of a single
shipper or a group of identical shippers.
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