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

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

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In the regression portion of his analysis Silberberg employs equa-<br />

tions of the following sort to estimate barge shipments from each of<br />

the twelve regions.<br />

Sw •.b+b I+b ( Rr - Rw ).<br />

(2.7) qi 0 lqi 2 qi qi<br />

Here<br />

q S s total tons of commodity i shipped by barge from<br />

i i<br />

region q,<br />

q I i<br />

is a measure of some economic activity to which barge<br />

shipments of commodity i are related,<br />

R. is the weighted average rail rate <strong>for</strong> commodity i<br />

q 1 from region q, and<br />

R w is the weighted average barge rate <strong>for</strong> commodity i<br />

q from region q.<br />

Similar equations were used to estimate quantities shipped by barge<br />

into each region. The major difference between the two sets of equa-<br />

tions lies in I,' the measure of related economic activity. The measures<br />

selected <strong>for</strong> the export equations were such things as production of the<br />

commodity in the region. The import equations, on the other hand, em-<br />

ployed indices that were thought to be more revealing of consumption<br />

levels;<br />

Both sets of equations required data on total shipments of each<br />

commodity into and out of each region. This in<strong>for</strong>mation was obtained<br />

from statistics published by the U. S. Corps of <strong>Army</strong> Engineers <strong>for</strong> •the<br />

period 1955 to 1961. 19 The equations also required data on barge and<br />

19. Corps of Engineers, United States Department of the <strong>Army</strong>,<br />

<strong>Water</strong>borne Commerce of the United'Statee, Supplement to Part 5, 1956 - 1961,<br />

Domestic Inland Traffic Areas of Origin and Destination of Principal<br />

Commodities.<br />

29

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