81
The quarterly observations were constructed from the published
secondary monthly data. Quarterly price, income, and index data were
constructed as unweighted three-month averages of the monthly data. To
obtain the quarterly price data, the monthly price series were simply
averaged over three-month periods for the years 1972 through 1981. An
attempt was made to use a weighted average for the ex-vessel series,
however, no significant gain was made relative to a three-month average
(the three-month average explained 99 percent of the variation in the
weighted average). Because of this, and since no reliable quantity
variable was available to properly weight the wholesale and retail
levels, a simple three-month average was used for all three quarterly
price series. Quarterly consumption, landings, and import data were
constructed as unweighted totals over the same three month intervals.
Beginning inventories on a quarterly basis, however, represent inven
tories at the beginning of the first month of each quarter.
Statistical Models
The exact specification of the monthly and quarterly price models
is conditional on the outcome of the first and second objectives as
outlined in Chapter I. The causality analysis will determine the direc
tion of price determination and, thus, what prices make up the subsets
of (equations 30 through 33) found in each price model.
The causality analysis must be completed before the system of price
models can be specified in terms of current and lagged exogenous and
endogenous prices. The following discussion of the price models ignores
the specification of found in each model and discusses the variables
which are given to be predetermined. A discussion of the final