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

of the barge coefficient seemed to follow the same pattern. The ex-
ponents of the labor-hours term appeared to fall over time. Hurter
recognized the possibility of strong collinearity between the fuel and
labor variables; he therefore examined the sum of the coefficients df
these variables as an indication of the effect of current inputs.
This sum was about 0.6 in 1962, 0.93 in 1957, and 1.3 in 1950, clearly,
according to Hurter, indicating a diminishing role for the current
inputs relative to the capital inputs. Relation (2) explained 75 to
90 percent of the observed variance in ton-miles.
In relationship (3), an upward trend in the exponent of the aver-
age horsepower variable seemed to indicate increasing importance of
- f
that variable; however, standard errors were large. The estimates of
the fuel coefficient were again uninformative, but the estimates of
the labor coefficients were quite stable and had reasonably large "t"
values. Equation (3) accounted for only 59 to 65 percent of the ob-
served variance in annual tonnage.
Relation (4), which differs from (3) through the introduction of
annual firm towboat mileage as an additional explanatory variable,
changed considerably from one year to the other. The standard errors
of the exponent estimates for the variable miles were very large ex-'
cept for 1962 when the exponent appeared positive and greater than
unity. The standard errors of the horsepower-per-towboat term were
too large to permit any discussion of their change over time. Other
.,
problems appeared in the estimates of this relation; e.g., the esti-
mate of the fuel coefficient was positive in 1957 but negative in
1962; the sum of the fuel and labor coefficients was 0.74 in 1950,
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