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Technical Note

   
   This release presents labor force and unemployment data for census
regions and divisions and states from the Local Area Unemployment
Statistics (LAUS) program.  The LAUS program is a federal-state co-
operative endeavor.
   
Concepts
   
   Definitions.  The labor force and unemployment data are based on the
same concepts and definitions as those used for the official national
estimates obtained from the Current Population Survey (CPS), a sample
survey of households that is conducted for the Bureau of Labor Sta-
tistics (BLS) by the U.S. Census Bureau.  The LAUS program measures
employment and unemployment on a place-of-residence basis.  The universe
for each is the civilian noninstitutional population 16 years of age and
over.  Employed persons are those who did any work at all for pay or
profit in the reference week (the week including the 12th of the month)
or worked 15 hours or more without pay in a family business or farm,
plus those not working who had a job from which they were temporarily
absent, whether or not paid, for such reasons as labor-management
dispute, illness, or vacation.  Unemployed persons are those who were
not employed during the reference week (based on the definition above),
had actively looked for a job sometime in the 4-week period ending with
the reference week, and were currently available for work; persons on
layoff expecting recall need not be looking for work to be counted as
unemployed.  The labor force is the sum of employed and unemployed per-
sons.  The unemployment rate is the number of unemployed as a percent
of the labor force.  The employment-population ratio is the proportion
of the civilian noninstitutional population aged 16 years and over that
is employed.
   
   Method of estimation.  Estimates for 48 of the 50 states, the
District of Columbia, the Los Angeles-Long Beach-Glendale metropolitan
division, New York City, and the balances of California and New York
State are produced using estimating equations based on regression tech-
niques.  This method, which underwent substantial enhancement at the
beginning of 2005, utilizes data from several sources, including the
CPS, the Current Employment Statistics (CES) survey of nonfarm payroll
employment, and state unemployment insurance (UI) programs.  Estimates
for the state of California are derived by summing the estimates for the
Los Angeles-Long Beach-Glendale metropolitan division and the balance of
California.  Similarly, estimates for New York State are derived by sum- 
ming the estimates for New York City and the balance of New York State.  
Estimates for all nine census divisions are based on a similar regression 
approach that does not incorporate CES or UI data.  Estimates for census 
regions are obtained by summing the model-based estimates for the com-
ponent divisions and then calculating the unemployment rate.  Each month, 
census division estimates are controlled to national totals; state esti-
mates are then controlled to their respective division totals.  Estimates 
for Puerto Rico are derived from a monthly household survey similar to 
the CPS.  A detailed description of the estimation procedures is available 
from BLS upon request.
   
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   Annual revisions.  Labor force and unemployment data for prior years
reflect adjustments made at the end of each year.  The adjusted esti-
mates reflect updated population data from the U.S. Census Bureau,
any revisions in the other data sources, and model reestimation.  In
most years, historical data for the most recent 5 years (both sea-
sonally adjusted and not seasonally adjusted) are revised near the be- 
ginning of each calendar year, prior to or coincident with the release
of January estimates.
   
Reliability of the estimates

   The estimates presented in this release are based on sample surveys,
administrative data, and modeling and, thus, are subject to sampling 
and other types of errors.  Sampling error is a measure of sampling
variability--that is, variation that occurs by chance because a sample
rather than the entire population is surveyed.  Survey data also are
subject to nonsampling errors, such as those which can be introduced
into the data collection and processing operations.  Estimates not
directly derived from sample surveys are subject to additional errors
resulting from the specific estimation processes used.  The sums of
individual items may not always equal the totals shown in the same
tables because of rounding.  Unemployment rates are computed from
unrounded data and thus may differ slightly from rates computed using
the rounded data displayed in the tables.
   
   Use of error measures.  In 2005, the LAUS program introduced several
improvements to its methodology.  Among these was the development of 
model-based error measures for the monthly estimates and the estimates 
of over-the-month changes.  Annual average error measures became avail-
able for the first time after 2006.  The introductory section of this 
release preserves the long-time practice of highlighting the direction 
of the movements in regional and state unemployment rates regardless 
of their statistical significance.  The remainder of the analysis in 
the release takes statistical significance into consideration.  Model-
based error measures are available online at http://www.bls.gov/lau/
lastderr.htm.  BLS uses a 90-percent confidence level in determining 
whether changes in LAUS unemployment rates are statistically significant.  
The average magnitude of the over-the-year change in an annual average 
state unemployment rate that is required in order to be statistically 
significant at the 90-percent confidence level is between 0.4 and 0.5 
percentage point.  More details can be found on the Web site.  Mea-
sures of nonsampling error are not available, but additional infor-
mation on the subject is provided in Employment and Earnings Online 
available on the BLS Web site at http://www.bls.gov/opub/ee/home.htm.

Additional information

   More complete information on the technical procedures used to develop
these estimates and additional data appear in Employment and Earnings
Online.
   
   Information in this release will be made available to sensory impaired 
individuals upon request.  Voice phone:  (202) 691-5200; TDD message re-
ferral phone:  1-800-877-8339.