2015 to 2040 Population Projections – County Level

June 29, 2018 edition

The Connecticut State Data Center provides population projections to assist state agencies, non-profit organizations, businesses, governments, and centers/organizations to identify demographic trends and changes within Connecticut. These projections are created based upon administrative and survey datasets and while these projections are developed based on the best data sources available, actual population changes may vary from these projections. To assist in planning, analysis, and decision making, the population projections have been developed based on state derived fertility rates.

The development of these population projections were funded by the Office of Policy and Management (OPM) with additional support provided by the UConn Library.

Summary  |  Usage and Limitations | Data Visualizations  | Data Tables  | Acknowledgements

Summary of the 2015 to 2040 Population Projections – County Level

The Connecticut State Data Center projections predict that just over half of the Counties in the state of Connecticut will experience a slight decline population from 2015 to 2040. The Windham County is expected to see the largest population increase in population of 11.26% by 2040. The Litchfield County is expected to experience the largest population decline of all of the Connecticut counties with a projected decline in population of 10.01% by 2040.

The slow projected growth and slight decline in population mirrors trends across the state of Connecticut and New England.


Population Projections Usage and Limitations

The population projections provide general statistical projections of the population by sex and five year age cohort from 2015 to 2040. The projections are based on birth and mortality data from the Connecticut Department of Public Health, migration data from the U.S. Census Bureau Population Estimates and American Community Survey (ACS), and population data from the U.S. Census Bureau Decennial Census. These projections provide population projections for individuals who are residents, or are projected to become, residents of the state of Connecticut. These projections are intended to guide planning, analysis, and decision making in the state and are reviewed on an annual basis to compare projections to the latest administrative and survey data available to identify if there are any significant deviations from the projected population to the observed population for the state of Connecticut.

These projections are based on an annual average of the resident population of the state of Connecticut. Resident population is defined as those persons who usually reside in the state of Connecticut (where they live and sleep most of the time). Individuals who reside in another state but either own property or work remotely in the state of Connecticut are not included in these population projections.

The projections are based on statistical models which utilize historical birth, mortality, and migration data to inform the model and the actual population numbers can be influenced by economic, policy, individual decisions, and other aspects which are not accounted for in the model.

Data Visualizations

To view trends in the population projections for Connecticut Counties, the Connecticut State Data Center has published a data story which provides the viewer with context of past trends and projected future trends. For each visualization, users can interact with the data and download an image of each visualization.


Data Tables

The Connecticut State Data Center has published these data tables to the State of Connecticut Open Data portal to allow users to download, visualize, filter, and connect to the data via APIs.

View and Download Data – Connecticut Open Data data.ct.gov


The development of the 2017-2018 edition of the population projections for the Regional Planning Organizations within the state of Connecticut is based on over 2 years of research testing different approaches, administrative and survey datasets, and models before the final projections were developed. This research involved a number of individuals and organizations and we want to acknowledge the following individuals/organizations for their assistance from providing data, to assisting and informing the methodology and approaches research, to developing the final projections, datasets, and visualizations which are available to the user.

Data Providers

Connecticut Department of Public Health, Connecticut Office of Policy and Management, Eversource, GeoLytics, Qualidigm, United Illuminating, U.S. Census Bureau

Dataset Development

Dr. Thomas Cooke (UConn Geography), Xiaojiang Li (CTSDC), Qinglin Hu (CTSDC) Wenjie Wang (CTSDC), Weixing Zhang (CTSDC)

Dataset Feedback and Guidance

Steve Batt (UConn Library), CABE, Dr. Thomas Cooke (UConn Geography), Hartford Data Meetup Group, Michael Howser (UConn Library)

Data Visualization

Steve Batt (UConn Library), Abraham Hilding Salorio (CTSDC)

Methodology and Research

Karyn Backus (CT DPH), Michael Howser (UConn Library), Qinglin Hu (CTSDC), Xiaojiang Li (CTSDC), Lloyd Mueller (CT DPH), UMASS Donahue Institute, Wenjie Wang (CTSDC), Weixing Zhang (CTSDC)

Funding and Reporting

Martha Bedard (UConn Library), Stephanie Beron (UConn Geography), Ed Chang (UConn Library), Michael Howser (UConn Library), Deborah Ives (UConn Sponsored Programs), Holly Jeffcoat (UConn Library), Tyler Kleykamp (OPM), MiChelle Lopes (UConn Sponsored Programs), Jillian Lopez (UConn Sponsored Programs), Ryan Marsalisi (UConn Library), Lori Mather (UConn Sponsored Programs)