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University of Connecticut Connecticut State Data Center

Connecticut Population Projections 2015-2025 FAQ

June 1, 2012 Edition


Which Fertility Rate Should I Select?

The Connecticut Population Projections 2015-2025 June 1, 2012 edition feature three fertility rates for each year of data and for each geography. Three fertility rates are provided as population projections represent an estimate of population within a geography and while projections provide a calculated estimate of population within a particular geography, population fertility rates may change due to a number of factors not easily accounted for in a population projection model. The three fertility rates provide users with a range of population scenarios to provide a visualization of the potential range of population change within a particular geography. Included below is a general overview of each of these fertility rate scenarios:

High Fertility Rate: This scenario assumes a high rate of population growth which based on recent trends in Connecticut's population is least likely to occur. The High Fertility rate scenario serves as a guide of what could happen if the selected geography experienced a baby boom type scenario

Medium Fertility Rate: This scenario assumes a medium rate of population growth.This scenario would be most likely for areas experiencing moderate growth

Low Fertility Rate: This scenario assumes a low rate of population growth. This scenario would be most likely for areas with slow population growth


Which Projection Should I Use?

Unlike decennial census data which represent counts of the population based on a comprehensive count, population projections provide an estimate of the potential population for a particular geography based on fertility, migration, and mortality calculations over time. While each projection is based on methods that produce as accurate of a population projection as statistically possible, changes in the local population dynamics (ex. increased in/out migration, increase/decrease in births due to socio-economic factors) can alter the population estimate for an area. As these projections are ESTIMATES, they should be treated as estimates and not an absolute number. Users should use the projections as a range of potential population changes within the geography you select. While we anticipate most geographies will experience a population change in the medium to low fertility scenario, users should examine all three estimates for each year closely to determine the potential range of population within an area.


Why Do Some of the Age Groups Have Zero People?

For a few of the age groups for specific geographies, you may encounter a "0" as the number of individuals estimated for the age group based on the population projections. This often indicates that the calculated migration rate for this age group results in creating a decrease in population in this age cohort and as a result this creates a "0" population for this age group. This is often a result of traditional college age students attending college resulting in an outward/inward migration value for this age group. In the upcoming months these areas will be examined more closely to identify additional methods to improve the overall population projections for towns with a sizable college age population.


How Frequently Will These Projections Be Updated?

The Connecticut State Data Center at the University of Connecticut Libraries Map and Geographic Information Center (MAGIC) anticipates reviewing the population projections on an annual basis to make adjustments to the methodology as necessary.


What Data Sources Were Used to Develop these Projections?

There are two sources of data for this analysis. The first is the U.S. Census. Table Q1-P1 was downloaded from the American Fact Finder 2 for both the 2000 and 2010 Decennial Census’. This table presents population by both age and gender, which is critical for this analysis. Birth and death data was acquired from the Connecticut Department of Public Health. Birth data was acquired in the form of number of births by age of mother in addition to births by gender.


How Can I View Additional Details on the Methodology?

Details on the methodology utilized to create the 2015-2025 Population Projections including the methods for calculating migration, fertility rates, and software are available on the Methodology page.




The development of these population projections were funded by the Office of Policy and Management (OPM).