Population of Michigan Counties by Age: 2000-2009  

Data Tables

County Population by 5-Year Age Group: Michigan, 2009
County Population by 5-Year Age Group: Michigan, 2008 
County Population by 5-Year Age Group: Michigan, 2007 
County Population by 5-Year Age Group: Michigan, 2006 
County Population by 5-Year Age Group: Michigan, 2005 
County Population by 5-Year Age Group: Michigan, 2004 
County Population by 5-Year Age Group: Michigan, 2003 
County Population by 5-Year Age Group: Michigan, 2002 
County Population by 5-Year Age Group: Michigan, 2001 
County Population by 5-Year Age Group: Michigan, 2000 
County Population by 5-Year Age Group: Michigan, April 2000 Estimates Base 
County Population by 5-Year Age Group: Michigan, April 2000 Census 

Analysis

Revisions to Prior Estimates of 2008 County Age Distribution (spreadsheet)
Revisions to Prior Estimates of County Age Distribution (text analysis)

Important Revisions to Prior Estimates
of County Age Distribution

The estimates of county population by 5-year age group that were released by the Census Bureau in June, 2010 include very large revisions to figures released in prior years. (Click here to view spreadsheet.)

The new estimates reflect each county's pattern of migration by age, which is measured primarily by matching every Social Security number from federal tax returns submitted in consecutive years and then analyzing any changes in address. Although the population estimates released in prior years did reflect each county's own total level of in-migration and out-migration from such an analysis, they reflected age distributions of in-migrants and out-migrants that had been computed at the statewide level.

(Each county's own distribution of migrants by race, sex and Hispanic origin has been reflected in both the new and the old estimates, however, and both sets of figures also reflect migration adjustments for college counties.)

The revisions to the previous estimates for 2008 are sometimes very large at the county level: 56 of Michigan's 83 counties have revisions in excess of 20% for one or more age groups, and 11 of these counties have revisions in excess of 40%. At the statewide level, there has been a small shift of estimated population from ages 25-34 (-2.7%) to ages 20-24 (+1.9%) and ages 65-84 (+1.9%)

The pattern of revisions is described below for several types of county and several age groups.

Central Metropolitan Counties

Several of Michigan's large central metropolitan counties have upward revisions for young adults age 25-34 and downward revisions for older working-age adults. Some of these revisions exceed 10 or even 20 percent. A majority of counties in this category have downward revisions for ages 55-69, but all of them have upward revisions for ages 70-84.

The 6 counties with upward revisions for age 25-29 (Kent, Oakland, Wayne, Macomb, Ottawa, and Saginaw) represent slightly more than 50 percent of Michigan's total population. The upward revisions for this age group include 22 percent increases for both Kent and Oakland counties and 15 percent increases for Wayne county and for the Detroit tri-county area as a whole. Michigan's remaining 77 counties had downward revisions for age 25-29.

University Counties

The estimated number of people age 20-24 has been revised upward by 18 percent or more for the seven Michigan counties with very high portions of their population in college (Houghton, Ingham, Isabella, Kalamazoo, Marquette, Mecosta, and Washtenaw). Those revisions are offset by large downward revisions for ages 25-34 and (in the case of Ingham, Kalamazoo, and Washtenaw counties) for older working-age adults as well. These revisions reflect an interaction between the adjustments applied to university counties and the new migration rates derived from income tax returns. The appropriateness of these adjustments is under review, and these estimates may be corrected in the future.

Fringe Metropolitan Counties

Fringe metropolitan counties-- non-central counties of Metropolitan Statistical Areas and small MSA's that are part of Combined Statistical Areas-- have generally had upward revisions for children, large downward revisions between the ages of 20 and 34, and upward revisions for most age groups from 35 to 84. An exception is Washtenaw county, where a large upward revision for age 20-24 has been offset by decreases below age 15 and for most age groups between 25 and 74.

Non-Metropolitan Counties

Michigan's non-metropolitan counties tend to have very large downward revisions for young adults. All of these counties have downward revisions for age 25-29, and a majority of those revisions exceed 20 percent. Almost all of these counties also have substantial downward revisions for age 30-34, and those without universities tend to have downward revisions for age 20-24 as well. Most counties in the northern Lower Peninsula also have downward revisions for age 35-39. Michigan's non-metropolitan counties generally have small upward revisions for ages 40-54 and larger upward revisions for ages 55-69. Their pattern is mixed for ages 70-84.

Ages 0 to 19

The revisions are smaller for children than for other age groups. Only 7 small counties have revisions of 10 percent or more for any of the 5-year age groups under age 20. The estimated number of children has been revised upward in all of Michigan's fringe metropolitan counties with the exception of Washtenaw, but the pattern is mixed for central metropolitan counties and non-metropolitan counties.

Ages 20-24

With the notable exception of university counties, estimated population levels for age 20-24 have been revised downward for most fringe metropolitan and non-metropolitan counties. These changes are offset by upward revisions for most university counties and a few additional central metropolitan counties. This pattern may change in future data releases, since the Census Bureau is planning additional refinements to its population adjustments for university counties.

Ages 25-34

The estimated number of people age 25-29 has been revised downward for all 69 of Michigan's fringe metropolitan and non-metropolitan counties. All but 5 of these reductions exceed 10 percent and 11 of them exceed 40 percent. Among Michigan's 14 central metropolitan counties, however, 6 have upward revisions, 6 have downward revisions of less than 10 percent, and two have downward revisions between 10 and 14 percent. The counties with upward revisions represent slightly more than 50 percent of Michigan's total population. .

The pattern is similar for age 30-34, with upward revisions for only 7 central metropolitan counties and 6 other counties scattered around the state.

In general, the central metropolitan counties that attract young adult workers tend to have upward revisions or small downward revisions for these age groups while fringe metropolitan counties and non-metropolitan counties that attract older workers and retirees tend to have large downward revisions.

Ages 35-49

Revisions are fairly small for ages 35-49, with only 5 counties having revisions as large as 10 to 15 percent for any of their age groups within this range. Fringe metropolitan counties and non-metropolitan counties in the southern Lower Peninsula have upward revisions or, in a few cases, small downward revisions over this entire age range. Most counties in the northern Lower Peninsula have downward revisions for age 35-39 and upward revisions for the older age groups. The pattern for central metropolitan counties and Upper Peninsula counties is mixed, with upward revisions in about half of the counties and downward revisions in the remainder.

Ages 50-69

Nearly all non-metropolitan counties have had upward revisions in this age range, and many of these revisions exceed 20 percent. The revisions tend to be smaller for metropolitan counties and they are split fairly evenly between increases and decreases..

Ages 70-84

Most metropolitan counties have had small upward revisions in this age range. However, about half of the counties in the southern Lower Peninsula and Upper Peninsula have had small downward revisions. Nearly all counties in the northern Lower Peninsula have had downward revisions for ages 75-84.

Age 85+

Nearly all counties have had downward revisions for this age group due to higher mortality estimates nationwide, and most of these downward revisions exceed 10 percent. About half of the fringe metropolitan counties have had upward revisions for this age group, however, including a 17 percent increase for Livingston county.