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Utilizing ACS 1-year and 3-year Data. Jerry Deichert and David Drozd Nebraska SDC National SDC Meeting, October 2009. Reasons for Using 3-year Data. Expanded geographic coverage Smaller error, especially for subgroups PUMS is three times larger (3 percent compared with 1 percent).
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Utilizing ACS 1-year and 3-year Data Jerry Deichert and David Drozd Nebraska SDC National SDC Meeting, October 2009
Reasons for Using 3-year Data • Expanded geographic coverage • Smaller error, especially for subgroups • PUMS is three times larger (3 percent compared with 1 percent)
Population Size • Nebraska, like many states with large rural populations, has few areas with 65,000+ population Area65,000+20,000-64,999 • Counties 3 16 • Cities 2 11 • Metros 3 3 • Micros 1 10 • School Districts 3 15 • PUMAs 14 14
Comments • Overlapping time periods • Income is for previous 12 months • Initial release of multi-year estimates is of prime importance; afterwards only 1 of 3 years of data changes • Last year’s new 3-year estimates had great interest (first new data since 2000 for many areas), little interest this year • More useful as cross-sectional rather than time series • Numbers are not consistent with most recent population estimates • Small areas may have extreme volatility in economic measures, not reflected in three year period • Small areas still may have large MOEs, especially for subgroups
3-year Estimates Allow for Analysis of Subgroups with Large MOE: Black Poverty in Omaha Metro YearPercentMOERank* 2005 40.4 4.8 3rd Highest of 87 2006 29.7 5.2 25th Highest of 95 2007 36.7 5.9 6th Highest of 99 2005-07 35.7 3.5 4th Highest of 100 2008 30.3 5.5 18th Highest of 96 * Rank is among the largest 100 metros at that time
Comments • Because of sampling error, there may be large differences in yearly point estimates that influence the 3-year estimate • What is the true level in reality? Which estimate was more likely to be correct – 40% or 30% in poverty • 3-year estimate may mask important changes that are occurring • Numbers can not be used for counts, relying on percentages appears more appropriate
Comparison of Nebraska Net Migration (using ACS B07000 & B07400 series) Variable2007 1-yr2005-07 3-yr Net Movement - 1,754 - 2,581 Male - 235 - 2,652 Female - 1,519 + 71 Hispanic - 2,336 + 752 White, NH +5,324 - 1,888 Under age 18 - 2,063 + 32 Age 40+ - 2,577 - 903 Bachelor’s + - 1,581 - 1,493
Comments • 3-year estimates may be difficult to interpret, what does net migration over the 3-year period mean? • Numbers are not consistent with most recent population estimate methodology • Changes to the methods to define net international inmigration could have impacted especially the Hispanic/Latino figures