|
DRAFT (DATA) APPENDIX
<br />A slightly different technique is used to project the populations of the youngest 10 age groups (0,
<br />1, 2,..., 9). First, births by race for each year of the decade are obtained by applying projected age
<br />and race specific birth rates for each year to previously projected numbers of women of child -
<br />bearing ages. Deviations in individual county birth rates from the corresponding state birth rates
<br />are set for future years based on averages over several (usually 5, occasionally 4 or 3) prior years
<br />for which actual birth counts are available. Second, sex -at -birth and survival rates are applied to
<br />the projected births to obtain projection date populations for those who were born within the
<br />county. Third, a special survived migration is added to these populations to account for children
<br />who moved to or from the county since they were born. This survived migration is calculated in
<br />a similar manner to that for the older age groups, except that the time period varies from 0.5 to
<br />9.5 years, depending on the age group being projected, always beg nnmg_at birth and ending at
<br />the end of the decade.
<br />INSTITUTIONAL EFFECTS
<br />The basic county trend projections produced for this series were modified for the growth of
<br />certain institutions. Institutions such as colleges, universities, military installations, and, to a
<br />lesser extent, prisons and some state hospitals, house persons of particular age groups. These
<br />populations will substantially grow or decline only by administrative action. There are thirteen
<br />counties in North Carolina the age structure of which is significantly affected by institutions.
<br />These counties (with major institution type) are Avery (prisons and college), Craven (military),
<br />Cumberland (military), Durham (university), Jackson (university), Madison (university), New
<br />Hanover (university), Onslow (military), Orange (university), Pasquotank (university and
<br />prisons), Pitt (university), Wake (university and prisons), and Watauga (university).
<br />Many counties, as well as the state as a whole, experienced some growth in institutional
<br />populations between 2000 and 2005. Roughly 2/3 of the increase was in Onslow County, one of
<br />the two counties with large military bases. The other county with a large military base;
<br />Cumberland, showed a large increase from 2000 to 2003, follwed by a much larger decrease
<br />from 2003 to 2005. It was assumed that all institutional populations would remain constant after
<br />2005.
<br />PROJECTION CONTROLS
<br />Three types of Projection controls were used. The first set was based totally on county estimates.
<br />Projected values for July 2000, July 2001, July 2002, July 2003, and July 2004 were controlled
<br />to revised county estimates for the corresponding dates. Projected values for 2005 were
<br />controlled to the set of July 2005 Provisional County Estimates released in May of 2006 by the
<br />State Demographer.
<br />The second set were county population controls for July 1st of each year from 2006 through
<br />2009 and for April 1, 2010. They were calculated in several steps. First, the "trend" growth from
<br />one projection date to the next was calculated by making a projection for the first projection
<br />decade without using any population controls. Second, the average annual non institutional
<br />population growth for 2000 -05, for 2004 -05, and for 2003 -05 were calculated from the Jules
<br />Provisional County Estimates, the July 2004 Revised County Estimates, the July 2003 Revised
<br />County Estimates, and the 2000 Census counts. Third, the "trend" growth and the "estimate"
<br />growth for each period (for July 2005 -July 2006, the non - institutional July 2004 -July 2005
<br />10
<br />8/16/2007
<br />
|