major determinant of the level of migration that in turn
is an important determinant of population levels. Projec-
tions of population, household, and employment levels
for the Region were thus prepared and evaluated concur-
rently using internally consistent and mutually support-
ive methodologies.
To deal with the uncertainties inherent in making long-
range projections, the Commission prepared alternative
high-growth, intermediate-growth, and low-growth projec-
tions of population, household, and employment levels
to reflect a reasonable range of demographic and economic
activity. This range of projections is useful for the devel-
opment of robust system plans at the regional level, as well
as facility plans at the local level. Plans developed using
the range of projections may be expected to remain viable
under greatly varying future conditions.
Population Projections
The technique selected by the Commission for developing
population projections is known as the cohort survival
technique. This technique takes into consideration base
year population and future rates of birth, death, and migra-
tion. Three different projections were made using different
combinations of assumed fertility, mortality, and migration
rates in an attempt to determine the population of the
Region under a range of possible future conditions.
Although fertility rates exhibited a moderate increase
during the 1980s, age-specific fertility rates in the Region,
State, and Nation are currently at some of the lowest levels
ever observed, and the total fertility rate is currently below
the replacement level in all three of these geographic areas.
While most demographers do not anticipate a return to
the high fertility levels observed in the period from 1945
to 1965, there is uncertainty about whether fertility will
remain at its current low level, continue to increase, or
begin again to decrease. It was assumed that fertility rates
would continue to increase gradually under a high-growth
scenario; remain virtually constant under an intermediate-
growth scenario; and decrease gradually under a low-
growth scenario.
The mortality rates used in all of the projections are
based upon the U. S. Social Security Administration life-
expectancy tables, with survival rates adjusted to account
for any differences in survival rates between Wisconsin
and the Nation. The survival rates utilized in the year 2020
population projections assume continuation of recent
trends toward slightly decreased mortality, particularly in
some of the older age groups, and are reflective of longer

life expectancies.

Migration is linked to both demographic and economic
factors, the latter including job availability, personal
income levels, and labor force participation rates. The
complex interrelationship between migration and other
demographic and economic factors is only partially under-
stood, and the determination of future migration levels
and patterns is always an uncertain process for areas such
as the Southeastern Wisconsin Region. Three different
regional net migration rates, based upon the high-growth,
intermediate-growth, and low-growth economic projec-
tions for the Region, combined with factors such as the
rate of multiple job holding, assumed future unemploy-
ment rates, and assumed future labor force participation
rates, were considered in the range of population projec-
tions for the Region.
Household Projections
Accompanying the changes in the size of the resident
population of the Region under three alternative population
projections are changes in the number and average size of
households in the Region. Household sizes have been
decreasing in the Region since 1950 owing to stable or
low fertility rates, increases in the number of single-parent
families, and changes in the age composition of the
population. Under the high-growth regional population
scenario, it is assumed that "traditional" households con-
sisting of couples with children will constitute the domi-
nant type of household. Under the intermediate-growth
scenario, it is assumed that traditional households will be
less dominant, and that single-parent and single-person
households will be more prevalent than under the high-
growth scenario. Under the low-growth scenario, it is
assumed that traditional households will continue to
decrease as a proportion of total households, and that
single-parent and single-person households will continue
to increase as a proportion of total households as they have
done historically.
Employment Projections
The regional employment projections for the year 2020
were developed using the dominant/subdominant-industry
methodology, which is a disaggregate technique dealing
separately with various components, or industries, of
the economic system. Under this approach, separate
projections were made for each of the dominant and
subdominant industry groups2 within the Region. Employ-
ment outside of those industry groups not accorded
2Dominant industry groups, as defined by the Regional
Planning Commission, account for 4 percent or more of
total regional employment, while subdominant industry
groups account for 2 percent to 3.9 percent of total

regional employment.

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