Life Expectancy: North Carolina 1990-1992 and 2005-2007, State and County
Life Expectancy (LE) is the average number of additional years that someone at a given age would be expected to live if he/she were to experience throughout life the age-specific death rates observed in a specified reference period (in this case, 1990-1992 or 2005-2007). Of course, death rates in the future are unknown and can be affected (positively or negatively) by new medical knowledge and procedures, better health conditions and practices, disease epidemics, and natural or man-made disasters (which would change the calculated LEs).
LEs are commonly presented in either Complete Life Tables (for individual years of age) or in Abridged Life Tables (for selected age intervals). The following Abridged Life Tables provide LEs for nineteen age intervals from infancy (<1) to ages 85+. In the Abridged Life Tables, LEs are calculated at the initial age for each age interval: at birth for ‘< 1 year’, 1 year old for ‘1 to 4’, etc. The LE estimates are calculated using NCHS Bridged population estimates and Vital Records death counts by reference year (1990-1992 or 2005-2007) by age interval by gender and/or race for the State of North Carolina and by county of residence. LEs are computed (using a procedure developed by Chiang1) for a specific reference year in a series of steps:
- Compute death rates (Mx) for each age interval, demographic, and geographic category by dividing the appropriate number of deaths by the population estimate.
- Calculate the number of persons alive (Ix) in each age interval assuming a base population of 100,000 newborns and the death rates for each age interval.
- Calculate the number of persons dying (Dx) during an age interval and the number of persons living at the end of each age interval.
- Calculate the number of years (Tx) that the base population has lived in each age interval and is expected to live in all subsequent age intervals.
- Calculate the life expectancy by dividing Tx by Ix for each age interval.
At the state level, the LEs are provided for each age interval (1) in total, and by (2) gender, (3) race (white and African American), and (4) race by gender. At the county level, the LEs are provided for each age interval (1) in total, and by (2) gender and (3) by race (white and African American). In counties with (1) a total African American population estimate of less than 1,000 or (2) any age interval population estimate less than 10, the LEs for African Americans are suppressed (labeled N/A) due to potential instability. Race-specific county-level LEs are limited to white & African American due to issues with small numbers for other racial and ethnic categories, such as American Indians and Hispanics. Previous studies have shown that American Indian race is under-reported on death certificates by as much as 20%,2 so the LEs not shown here for American Indians.
For questions or comments, contact Don Akin, State Center for Health Statistics, at (919) 715-4471 or don.akin@dhhs.nc.gov
1Chiang CL (1984) Life Table and Mortality Analysis, Malabar (FL), Robert E. Krieger Publishing Co.
2Buescher PA. Underreporting of American Indian race on North Carolina death certificates. Statistical Brief, No. 33, State Center for Health Statistics, North Carolina Division of Public Health, June 2007.
1990-1992 Life Expectancies Reports:
2005-2007 Life Expectancies Reports:
Page Last Updated August 31, 2009
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