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United States
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'I' Department of
Agriculture
National
Agricultural
Statistics
Service
Statistical
Research
Division
NASS Staff Report
Number YRB·88-05
June 1986
Corn Objective Yield:
An Empirical Evaluation
of the Use of 3, 4 or 5
Years Data. to Develop
Forecast Equations
Ronald J. Steele
Benjamin F. Klugh
CORN OBJECTIVE YIELD: AN
EMPIRICAL EVALUATION OF THE
USE
OF 3, 4 OR 5 YEARS'
DATA TO DEVELOP
FORECAST EQUATIONS.
By
Ronald J. Steele
and
Benjamin F. Klugh,
Statistical
Research
Division,
National
Agricultural
Statistics
Service, U.S. Department of Agriculture, Washington,
D.C.
20250, Staff Report No. YRB-Bo-05, June, 19Bo.
ABSTRACT
This study
compares the
level of
forecast errors
resulting
from using data from the
previous three, four and five
years
to develop forecast equations for corn yield.
Forecast errors
are tabulated for each state
and the ten state region
in the
corn objective
yield program
for the
years 1980-84.
These
tables provide a benchmark
of the performance of
the current
corn objective yield forecast procedures.
Analysis of variance procedures are used to test for
signifi-
cant differences
in the
level of
forecast errors
resulting
from
using
different
numbers
of
years of data to estimate
regression
relationships.
The
stability
of the estimated
regr.ssion parameters is assessed and discussed.
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This paper was prepared for limited distribution to
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*
the research community outside the U.S. Department
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*
of Agriculture.
The views expressed herein are not
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* necessarily those of NASS or USDA.
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i
TABLE OF CONTENTS
..............................................
SUMMARy ••••••
iii
I NTRODUCT I ON •••••••••••••••••••••••••••••••••••••••••••••••••
1
METHODOLOGY
••••••••••••••••••••••••
~ ••••••••••••••••••••••••.
1
ANALYSIS PROCEDURES
Forecast Errors •••••••••••••••••
Test for Treatment Differences •••••
Stability of Parameter Estimates •
·.
...
• •3
•5
• • 7
..
·.
RESULTS