WSP03577

• File Number: 8281.300
• Description: Colorado River Studies and Investigations - Colorado River Consumptive Uses and Losses Report
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 6/1/1991
• Title: Colorado Population Estimates and Projections 1980 - 2015
• Water Supply Pro - Doc Type: Report/Study

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employment. An exception to this general process of distribution was made for
the six counties of the Denver Metropolitan Area. Here, the regional employment
and labor force projections were distributed to each of the counties according
to distributions prepared in a 1988 forecast by the Denver Regional Council of
Governments.

The data requirements for running the model are: A) survival rates by age and
sex, B) fertility rates for women 15 - 49, C) net migration by age and sex, D)
base year population disaggregated by age and sex, and E) labor force
participation rates by age and sex. The model allows for changes in survival,
fertility, and labor force participation rates as well as migration rates and/or
amounts over time. The specific data and assumptions used in running the model
for these projections are described below. Questions about particular aspects
of these data should be addressed to Jim Westkott (866-3190). As adapted to the
Division's Prime Computer by Earl Hughes, this model can be run for any age group
or combination of age groups, and for any county or region or combination of
counties or regions to any year up to 2015. Remote computer access to model
output is available to subscribers to CEDIS (Colorado Economic and Demographic
Information System), the Demographic Section's online data service.

ASSUMPTIONS

The Demographic Section has made a number of estimates and assumptions in
applying this model to Colorado and its counties. These are described briefly
below:

Survival Rates. The number of deaths in each projection year is calculated by
applying a survival rate to each single year age-sex group. Base year survival
rates were derived by calculating annual average age- sex specific death rates.
Resident deaths for 1979 - 1981 constituted the numerator and the 1980 Census
population the denominator for each age-sex group. Survival rates are assumed
to improve slighlty over time, maintaining their current ratio to rates projected
by the Cen'sus Bureau for the U. S. (Current Population Reports, Series P-25, No.
1018, issued January, 1989). Expectation of life at birth for Colorado females
is assumed to increase from 78.8 years in 1980 to 81.7 years in 2010. Comparable
figures for males are 71.7 years in 1980 and 74.5 in 2010. A single set of
survival ~ates is used for all counties in the state.

Fertilitv ,Rates. The number of births in each projection year is calculated by
applying age specific fertility rates (by five year age groups) to the resident
female population 15 - 49. Fertility rates were derived by calculating the
annual average fertility rate using resident births for 1979 - 1981 as the
numerator and the 1980 Census female population in each age group as the
denominator. Fertility rates are assumed to increase slightly over time with
Colorado fertility rates maintaining their current ratio to the Census Bureau's
projected U. S. rates (Current Population Reports, Series P-25, No. 1018, issued
January, 1989.)

The total fertility rate for the State is expected to increase from 1778 births
per 1000 women 15 - 49 in 1980 to 1915 births per 1000 women 15 - 49 in 2010.
Because there is such greater regional variation in fertility rates than survival
rates different fertility rates are used for different counties in the state.
An examination of county-specific fertility rates for 1979 - 1981 resulted in the
creation of seven county groups which are relatively homogeneous with respect to
fertility.

County groups, constitutient counties, and estimated and projected rates are
shown in the table on the nex~ page.