3

Effective with the release of July 2001 data, official

labor force estimates from the Bureau of Labor Statistics (BLS) Current Population Survey (CPS) and

Local Area Unemployment Statistics (LAUS) program reflect the expansion of the monthly CPS sample from about

50,000 to about 60,000 eligible households. This expansion

of the monthly CPS sample was one part of the Census

Bureau’s plan to meet the requirements of the State

Children’s Health Insurance Program (SCHIP) legislation.

The SCHIP legislation requires the Census Bureau to

improve State estimates of the number of children who live

in low-income families and lack health insurance. These

estimates are obtained from the Annual Demographic

Supplement to the CPS.

In September 2000, the Census Bureau began expanding

the monthly CPS sample in 31 states and the District of

Columbia. The additional 10,000 households were added

to the sample over a 3-month period. BLS chose not to include the additional households in the official labor force

estimates, however, until it had sufficient time to evaluate

the estimates from the 60,000-household sample. This

article discusses the impact of the sample expansion on

national labor force estimates and on the State and area

labor force statistics over the January-June 2001 period.

Effect of the sample expansion on national CPS

estimates

At the national level, the estimates (not seasonally adjusted)

derived from the 50,000- and 60,000-household samples

were virtually the same. In any given month, the 60,000-

household sample estimates for the overall labor force participation rate and the employment-population ratio differed

by no more than 0.1 percentage point from estimates produced from the 50,000-household sample. The overall unemployment rates were identical in both samples over the

period. (See table 1.)

A marginal benefit of the new sample is that it will slightly

improve the coefficient of variation on the national unemployment level, from about 1.9 percent to about 1.8 percent, assuming an unemployment rate of 6 percent. (The

coefficient of variation, or CV, is defined as the standard

error of the estimate divided by the estimate, expressed as a

percentage.) The relatively small improvement reflects the

allocation of the additional sample to less populous States

that have a smaller impact on the national coefficient of

variation. A simple across-the-board proportional increase

in State sample sizes would have resulted in a larger drop in

the CV at the national level.

As shown in table 1, there were only marginal differences

in the monthly labor force, employment, and unemployment

levels between the two samples. Estimates from both samples

were examined for other data series as well, such as occupational employment, full- and part-time employment, and

multiple jobholding, and the differences over the JanuaryJune period appeared to be insignificant.

Among the major worker groups, labor force estimates

from the 50,000- and 60,000-household samples were

essentially the same over the January-June period. While

differences in the estimates for some population subgroups

may appear relatively large, they likely reflect the greater

known variance associated with estimates for these groups,

such as blacks, Hispanics, and teenagers.

At the national level, previously published monthly labor

force estimates for January to June will not be revised,

because the differences between the two samples were only

minimal. The 2001 annual averages for all labor force

series, however, will be calculated using the monthly average (January-December) from the expanded 60,000-household sample.

Effect of the sample expansion on LAUS State

estimates

At the State level, the sample expansion was not evenly distributed, but rather concentrated in States (and the District

of Columbia) with the least reliable March estimates of children in poverty without health insurance. States were identified for sample supplementation based on the standard error of their March estimate of low-income children without

health insurance.

The sample expansion resulted in substantial improvements in the quality of the State CPS data by reducing the

coefficient of variation on the monthly and annual average

labor force estimates. (See table 2, which provides the current CVs for all States and the resultant CVs for those States

Expansion of the Current Population

Survey Sample Effective July 2001

Ryan T. Helwig, Randy E. Ilg, and Sandra L. Mason

Ryan T. Helwig and Randy E. Ilg are economists in the Division of Labor

Force Statistics, Bureau of Labor Statistics. Telephone: (202) 691-6378;

e-mail: Helwig_R@bls.gov and Ilg_R@bls.gov. Sandra L. Mason is

a supervisory economist in the Division of Local Area Unemployment

Statistics, Bureau of Labor Statistics. Telephone: (202) 691-6392; e-mail:

Mason_S@bls.gov.
4

receiving the additional households.) The SCHIP expansion

did not result in systematically higher or lower labor force

values across the States.

The monthly State CPS employment and unemployment

estimates are not used directly, but instead are inputs to the

LAUS estimating models, which provide the “official” estimates of the State levels. For this reason, the impact of the

new sample on the model-based estimates also was analyzed. In comparing the old and new estimates, no systematic differences in the levels or in the direction of change

were found in either the CPS unemployment rates or the

model-based estimates. For the vast majority of monthly

comparisons between the old and new State samples, the

differences also were not statistically significant. Exceptions included the April unemployment rates for both Colorado and the District of Columbia and the January and March

unemployment rates for Connecticut.

While the sample expansion was not designed to reduce

error in the unemployment rate estimates, the substantial

sample increases in selected States have important implications for the LAUS models. These models are designed to

respond to changes in the reliability of the monthly State

CPS data. The “noise component” directly incorporates

measures of the magnitude (standard deviation) of the CPS

sampling error in the estimation process. More reliable CPS

data are given more weight in the estimation methodology.

When the CPS data are less reliable, the model estimates

depend more on historical patterns than on the current

monthly CPS data. This property of the LAUS models

allows them to exploit the SCHIP sample immediately. The

new, lower CPS standard deviations were fed into the models’ noise component, resulting in stronger weighting of the

combined-sample CPS in the model-based estimates for the

31 States and the District of Columbia.

States not involved directly in the sample expansion may

have small changes in their CPS estimates due to the

second-stage ratio adjustment procedure used in the CPS.

(For more information, see the “Explanatory Notes and

Estimates of Error” section in this issue of Employment and

Earnings.) Because the national sample estimates change

slightly due to the SCHIP-related sample expansion, small

adjustments to the sample weights in those States with no

sample expansion will be made to ensure conformity to national demographic controls. The impact on the CPS data

for these States, and on their model-based estimates, is minimal.

The new sample will be the basis for the July 2001 and

June 2001 revised estimates for all States, the District of

Columbia, New York City, and Los Angeles-Long Beach.

The LAUS additivity process forces sub-State employment

and unemployment estimates to equal their respective statewide totals. Therefore, beginning with July 2001/June 2001

revised data, sub-State estimates will reflect the new sample

through the additivity process. The new sample data for all

months of 2001 will be used to calculate the 2001 annual

average data that will appear in the 2001 Geographic Profile of Employment and Unemployment and in the 2001

benchmarking of State and sub-State labor force estimates.
5

Table 1. National labor force estimates using old and new CPS samples, January-June 2001, not seasonally adjusted

(Numbers in thousands)

Characteristic

January February March

Old New Difference Old New Difference Old New Difference sample sample sample sample sample sample

Civilian labor force

Total, 16 years and over ................................... 141,049 141,178 -129 141,238 141,263 -25 141,751 141,794 -43

16 to 19 years ............................................. 7,724 7,773 -49 7,765 7,802 -37 7,769 7,808 -39

Men, 20 years and over .............................. 71,161 71,225 -64 71,139 71,195 -56 71,251 71,284 -33

 Women, 20 years and over ........................ 62,164 62,181 -17 62,335 62,266 69 62,731 62,703 28

White........................................................... 117,622 117,754 -132 117,883 117,952 -69 118,166 118,185 -19

Black ........................................................... 16,577 16,583 -6 16,511 16,485 26 16,699 16,717 -18

Hispanic origin ............................................ 15,513 15,482 31 15,662 15,605 57 15,820 15,769 51

Participation rate

Total, 16 years and over ................................... 66.9 66.9 .0 66.9 66.9 .0 67.1 67.1 .0

16 to 19 years ............................................. 48.1 48.4 -0.3 48.2 48.5 -0.3 48.2 48.5 -0.3

Men, 20 years and over .............................. 76.4 76.4 .0 76.3 76.4 -.1 76.4 76.4 .0

Women, 20 years and over ......................... 61.2 61.2 .0 61.3 61.2 .1 61.6 61.6 .0

White........................................................... 67.1 67.2 -.1 67.2 67.3 -.1 67.4 67.4 .0

Black ........................................................... 65.3 65.3 .0 65.0 64.9 .1 65.6 65.7 -.1

Hispanic origin ............................................ 68.1 68.0 .1 68.6 68.4 .2 69.1 68.9 .2

Employed

Total, 16 years and over ................................... 134,462 134,605 -143 134,774 134,833 -59 135,298 135,287 11

16 to 19 years ............................................. 6,601 6,618 -17 6,655 6,692 -37 6,680 6,711 -31

Men, 20 years and over .............................. 68,101 68,174 -73 68,114 68,163 -49 68,171 68,152 19

Women, 20 years and over ......................... 59,760 59,813 -53 60,005 59,978 27 60,447 60,424 23

White........................................................... 112,768 112,925 -157 113,029 113,108 -79 113,445 113,420 25

Black ........................................................... 15,170 15,158 12 15,192 15,190 2 15,264 15,277 -13

Hispanic origin ............................................ 14,525 14,490 35 14,629 14,569 60 14,737 14,680 57

Part time for economic reasons .................. 3,693 3,793 -100 3,424 3,496 -72 3,338 3,290 48

Employment-population ratio

Total, 16 years and over ................................... 63.8 63.8 .0 63.9 63.9 .0 64.1 64.1 .0

16 to 19 years ............................................. 41.1 41.2 -0.1 41.3 41.6 -0.3 41.5 41.6 -0.1

Men, 20 years and over .............................. 73.1 73.2 -.1 73.1 73.1 .0 73.1 73.1 .0

Women, 20 years and over ......................... 58.8 58.8 .0 59.0 59.0 .0 59.4 59.4 .0

White........................................................... 64.3 64.4 -.1 64.5 64.5 .0 64.7 64.7 .0

Black ........................................................... 59.8 59.7 .1 59.8 59.8 .0 60.0 60.0 .0

Hispanic origin ............................................ 63.8 63.6 .2 64.1 63.8 .3 64.4 64.1 .3

Unemployed

Total, 16 years and over ................................... 6,587 6,573 14 6,464 6,430 34 6,453 6,507 -54

16 to 19 years ............................................. 1,123 1,155 -32 1,110 1,110 0 1,088 1,097 -9

Men, 20 years and over .............................. 3,060 3,050 10 3,025 3,032 -7 3,080 3,132 -52

Women, 20 years and over ......................... 2,404 2,367 37 2,329 2,288 41 2,285 2,278 7

White........................................................... 4,854 4,829 25 4,853 4,844 9 4,721 4,766 -45

Black ........................................................... 1,407 1,425 -18 1,319 1,294 25 1,435 1,439 -4

Hispanic origin ............................................ 989 991 -2 1,034 1,036 -2 1,083 1,089 -6

Unemployment rate

Total, 16 years and over ................................... 4.7 4.7 .0 4.6 4.6 .0 4.6 4.6 .0

16 to 19 years ............................................. 14.5 14.9 -0.4 14.3 14.2 0.1 14.0 14.1 -0.1

Men, 20 years and over .............................. 4.3 4.3 .0 4.3 4.3 .0 4.3 4.4 -.1

Women, 20 years and over ......................... 3.9 3.8 .1 3.7 3.7 .0 3.6 3.6 .0

White........................................................... 4.1 4.1 .0 4.1 4.1 .0 4.0 4.0 .0

Black ........................................................... 8.5 8.6 -.1 8.0 7.9 .1 8.6 8.6 .0

Hispanic origin ............................................ 6.4 6.4 .0 6.6 6.6 .0 6.8 6.9 -.1

See note at end of table.
6

Table 1. National labor force estimates using old and new CPS samples, January-June 2001, not seasonally adjusted—Continued

(Numbers in thousands)

Characteristic

April May June

Old New Difference Old New Difference Old New Difference sample sample sample sample sample sample

Civilian labor force

Total, 16 years and over ................................... 141,073 141,132 -59 141,048 141,192 -144 142,684 142,770 -86

16 to 19 years ............................................. 7,573 7,629 -56 7,639 7,710 -71 9,351 9,414 -63

Men, 20 years and over .............................. 71,409 71,424 -15 71,360 71,480 -120 71,627 71,696 -69

Women, 20 years and over ......................... 62,091 62,078 13 62,049 62,003 46 61,707 61,661 46

White........................................................... 117,572 117,678 -106 117,491 117,637 -146 118,859 118,938 -79

Black ........................................................... 16,576 16,540 36 16,608 16,610 -2 16,897 16,886 11

Hispanic origin ............................................ 15,712 15,682 30 15,592 15,579 13 15,669 15,662 7

Participation rate

Total, 16 years and over ................................... 66.7 66.8 -0.1 66.7 66.7 .0 67.4 67.4 .0

16 to 19 years ............................................. 47.1 47.4 -.3 47.6 48.0 -0.4 58.1 58.5 -0.4

Men, 20 years and over .............................. 76.4 76.5 -.1 76.3 76.4 -.1 76.5 76.6 -.1

Women, 20 years and over ......................... 61.0 60.9 .1 60.9 60.8 .1 60.5 60.4 .1

White........................................................... 67.0 67.0 .0 66.9 67.0 -.1 67.6 67.7 -.1

Black ........................................................... 65.1 64.9 .2 65.1 65.1 .0 66.2 66.1 .1

Hispanic origin ............................................ 68.4 68.3 .1 67.7 67.7 .0 67.9 67.8 .1

Employed

Total, 16 years and over ................................... 135,122 135,151 -29 135,202 135,340 -138 135,923 136,005 -82

16 to 19 years ............................................. 6,563 6,624 -61 6,627 6,683 -56 7,797 7,833 -36

Men, 20 years and over .............................. 68,644 68,624 20 68,772 68,884 -112 68,910 68,974 -64

Women, 20 years and over ......................... 59,915 59,903 12 59,804 59,773 31 59,215 59,198 17

White........................................................... 113,162 113,249 -87 113,261 113,408 -147 113,926 114,005 -79

Black ........................................................... 15,334 15,296 38 15,314 15,321 -7 15,434 15,436 -2

Hispanic origin ............................................ 14,761 14,732 29 14,707 14,693 14 14,640 14,636 4

Part time for economic reasons .................. 3,108 3,165 -57 3,270 3,237 33 3,924 3,964 -40

Employment-population ratio

Total, 16 years and over ................................... 63.9 63.9 .0 63.9 64.0 -0.1 64.2 64.2 .0

16 to 19 years ............................................. 40.8 41.1 -0.3 41.3 41.6 -.3 48.5 48.6 -0.1

Men, 20 years and over .............................. 73.5 73.5 .0 73.5 73.6 -.1 73.6 73.7 -.1

Women, 20 years and over ......................... 58.8 58.8 .0 58.7 58.6 .1 58.0 58.0 .0

White........................................................... 64.5 64.5 .0 64.5 64.6 -.1 64.8 64.9 -.1

Black ........................................................... 60.2 60.1 .1 60.1 60.1 .0 60.4 60.5 -.1

Hispanic origin ............................................ 64.3 64.2 .1 63.9 63.8 .1 63.4 63.4 .0

Unemployed

Total, 16 years and over ................................... 5,951 5,982 -31 5,846 5,852 -6 6,762 6,765 -3

16 to 19 years ............................................. 1,010 1,005 5 1,013 1,027 -14 1,554 1,581 -27

Men, 20 years and over .............................. 2,765 2,801 -36 2,588 2,595 -7 2,716 2,721 -5

Women, 20 years and over ......................... 2,175 2,176 -1 2,245 2,229 16 2,492 2,462 30

White........................................................... 4,410 4,429 -19 4,230 4,229 1 4,932 4,933 -1

Black ........................................................... 1,242 1,244 -2 1,294 1,289 5 1,463 1,450 13

Hispanic origin ............................................ 951 950 1 885 886 -1 1,029 1,026 3

Unemployment rate

Total, 16 years and over ................................... 4.2 4.2 .0 4.1 4.1 .0 4.7 4.7 .0

16 to 19 years ............................................. 13.3 13.2 0.1 13.3 13.3 .0 16.6 16.8 -0.2

Men, 20 years and over .............................. 3.9 3.9 .0 3.6 3.6 .0 3.8 3.8 .0

Women, 20 years and over ......................... 3.5 3.5 .0 3.6 3.6 .0 4.0 4.0 .0

White........................................................... 3.8 3.8 .0 3.6 3.6 .0 4.1 4.1 .0

Black ........................................................... 7.5 7.5 .0 7.8 7.8 .0 8.7 8.6 .1

Hispanic origin ............................................ 6.1 6.1 .0 5.7 5.7 .0 6.6 6.6 .0

NOTE: Detail for the above race and Hispanic-origin groups will not

sum to totals because data for the “other races” group are not presented and Hispanics are included in both the white and black population groups.
7

Table 2. Old and new CPS sample size by State, and coefficients of variation on the annual average level of unemployment

Number of households CV using old Expected CV

State Old CPS Additional CPS New CPS sample1 using new Percent

sample size sample size sample size (percent) sample1 change in CV

(percent)

Alabama ............................................. 910 210 1,120 7.221 6.544 -9.4

Alaska ................................................ 880 270 1,150 7.414 6.503 -12.3

Arizona ............................................... 820 0 820 6.952 6.952 .0

Arkansas ............................................ 920 0 920 7.214 7.214 .0

California ............................................ 4,260 0 4,260 2.930 2.930 .0

Colorado ............................................. 820 550 1,370 7.020 5.821 -17.1

Connecticut ........................................ 600 600 1,200 7.658 5.415 -29.3

Delaware ............................................ 700 260 960 7.364 6.280 -14.7

District of Columbia ............................ 780 190 970 7.993 7.149 -10.6

Florida ................................................ 3,180 0 3,180 3.711 3.711 .0

Georgia .............................................. 970 0 970 6.255 6.255 .0

Hawaii ................................................ 540 290 830 7.760 6.411 -17.4

Idaho .................................................. 1,040 0 1,040 6.827 6.827 .0

Illinois ................................................. 2,320 0 2,320 4.186 4.186 .0

Indiana................................................ 830 500 1,330 6.972 5.701 -18.2

Iowa .................................................... 780 400 1,180 7.245 6.208 -14.3

Kansas ............................................... 870 450 1,320 7.325 6.249 -14.7

Kentucky ............................................ 820 190 1,010 7.203 6.533 -9.3

Louisiana ............................................ 850 0 850 7.028 7.028 .0

Maine ................................................. 780 660 1,440 7.592 5.682 -25.2

Maryland ............................................ 770 510 1,280 7.146 5.688 -20.4

Massachusetts ................................... 1,330 0 1,330 5.012 5.012 .0

Michigan ............................................. 1,980 0 1,980 4.471 4.471 .0

Minnesota ........................................... 860 450 1,310 7.281 6.348 -12.8

Mississippi .......................................... 770 0 770 7.327 7.327 .0

Missouri .............................................. 790 360 1,150 7.111 5.896 -17.1

Montana ............................................. 900 0 900 7.206 7.206 .0

Nebraska ............................................ 790 350 1,140 7.151 6.300 -11.9

Nevada ............................................... 890 400 1,290 7.034 5.839 -17.0

New Hampshire .................................. 660 660 1,320 7.531 5.325 -29.3

New Jersey ........................................ 1,690 0 1,690 4.431 4.431 .0

New Mexico ........................................ 830 0 830 7.215 7.215 .0

New York ............................................ 3,730 0 3,730 3.240 3.240 .0

North Carolina .................................... 1,650 0 1,650 5.588 5.588 .0

North Dakota ...................................... 880 360 1,240 7.417 6.512 -12.2

Ohio.................................................... 2,170 0 2,170 4.397 4.397 .0

Oklahoma ........................................... 960 120 1,080 7.426 7.100 -4.4

Oregon ............................................... 750 380 1,130 7.319 6.125 -16.3

Pennsylvania ...................................... 2,620 0 2,620 4.134 4.134 .0

Rhode Island ...................................... 620 630 1,250 7.752 5.482 -29.3

South Carolina .................................... 720 280 1,000 7.406 6.396 -13.6

South Dakota...................................... 870 380 1,250 7.108 6.295 -11.4

Tennessee .......................................... 850 90 940 7.011 6.636 -5.3

Texas .................................................. 2,680 0 2,680 3.615 3.615 .0

Utah .................................................... 690 90 780 7.113 6.803 -4.4

Vermont .............................................. 770 650 1,420 7.331 5.353 -27.0

Virginia ............................................... 950 240 1,190 6.833 6.236 -8.7

Washington ........................................ 740 510 1,250 7.582 6.317 -16.7

West Virginia ...................................... 970 220 1,190 7.068 6.365 -9.9

Wisconsin ........................................... 900 550 1,450 7.392 6.301 -14.8

Wyoming ............................................ 890 220 1,110 7.294 6.699 -8.2

1 Coefficient of variation for the annual average estimated level of

unemployment, assuming a 6 percent unemployment rate.