Model-Based County Population Estimates

.. determining “where we are now” and “about recent trends” … what is the natural increase (population change due to births less deaths only, without considering migration) in the population from year to year or over several years, for counties/regions of interest? Does the county net migration reflect population moving in or out? Is there a migration pattern/trend? What factors are responsible for migration? To know about these patterns, characteristics and trends, requires annual, up-to-date population estimates.

Population Estimates & Components of Change
The following graphic shows population estimates and components of change for Harris County, TX. Similar profiles are available for all counties; read on.

Click graphic for larger view

Census Bureau Model-Based Population Estimates
Each year the Census Bureau develops model-based estimates of the population by county. The post-census estimates are intended to provide updates to Census 2019. The estimates provide an update and more current picture of the population size, composition and how it is changing. In March 2014, the U.S. by county July 1, 2013 population estimates and components of change became available. In June 2014, the U.S. by county July 1, 2013 population estimates with breakouts by age, gender and race/origin will become available. The model-based estimates, also referred to as synthetic estimates, are separate from the annual American Community Survey (ACS) data that provides similar annual population estimates.

First of Four Sections
This section is the first of four parts focused on the structure/content, access, use and evaluation of the annual Census Bureau model-based county population estimates. This section is focused on the structure/content and access to the population estimates and components of change. The next section (June) will focus on age and race/ethnicity detail. The third section (July) will focus on use: interpretation, geospatial/visual pattern analysis/mapping with GIS tools and time series/trend analysis. The fourth section (August) will focus on comparing the Census Bureau model-based estimates to alternative estimates.

Population Estimates and Components of Change
Model-based population estimates are developed using the population identity:

P[t] = P[t-1] + B[t-1,t] – D[t-1,t] + M[t-1,t]

The population at time t (July 1, 2013) is defined as the population at time t-1 (July 1, 2012) plus births (B) occurring from time t-1 to time t, less deaths (D) occurring from time t-1 to time t, plus net migration (M) occurring from time t-1 to time t. Migration is defined as the sum of the net international migration (MI) plus net domestic migration (MD):

M[t-1,t] = MI[t-1,t] + MD[t-1,t]

Population Estimates & Components of Change Interactive Table
Use the interactive table to examine the Census 2010 population (4/1/2010 column) and annual population estimates (7/1/2010 through 7/1/2013) for all counties and metros. Each row presents the same population estimates and components of change data as shown in the profile at the top of this section. The standalone county profile will be expanded in related (upcoming) sections to show 1) alternative estimates and components of change and 2) addition of population estimates by age, gender and race/origin.

County profiles are available for any county by clicking the link in the interactive table. The Census Bureau model-based estimates will update with 2014 estimates scheduled to become available in March 2015. While these tables show data developed by the Census Bureau, most of these data are available only in data files that require processing to organize the data into a usable form.

Support & DMI Web Sessions
Learn more about using resources described in this section. Join us in a Decision-Making Information Web session. There is no fee for these one-hour Web sessions. Each informal session is focused on a specific topic. The open structure also provides for Q&A and discussion of application issues of interest to participants. We can address your specific questions about using metro and county demographic economic data and related applications.


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