acs pums – how to aggregate sample

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ACS PUMS – How to Aggregate Sample

Anthony Tersine

US Census Bureau

Census Information Center Meeting

October 10, 2007

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ACS PUMS - Sampling

• 2005 PUMS is limited to housing units and household population

• 2006 PUMS includes housing units, household population and the group quarters population

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Multiyear PUMS Files

• Two approaches – both combine single year files

1. Adjust estimates at the end

2. Adjust weights at the beginning

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Method 1

• Concatenate single year files

• Adjust dollar amounts for inflation

– Express prior year dollars in terms of

latest year dollars

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Adjust Dollar Amounts – 1

• First apply “ADJUST” variable within year

• Apply the CPI-U-RS adjustment factors from BLS

• http://www.bls.gov/cpi/cpiurs1978_2006.pdf

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Adjust Dollar Amounts – 2

• Express year 2005 dollars in terms of 2006 dollars

• Values from the CPI-U-RS table for 2005 (286.7) and 2006 (296.1)

• Multiply the 2005 dollars by 296.1/286.7 = 1.03279

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Adjust Dollar Amounts – Example

• 2005-2006 person income in 2006 $

• 2005 person record

PINC * (ADJUST / 1000000) * 1.03279

• 2006 person record

PINC * (ADJUST / 1000000)

• ADJUST – different values

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Method 1 –Tabulations

• Use combined file as a single-year file• Adjust estimates based on number of

years (M) combining• Create counts, means, medians, etc.

– Create separate estimates for HU and GQ persons

• Standard Errors– Replicate weights– Generalized variances

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Method 1 – Counts / Aggregates

• All years have GQs or only interested in HU or household pop

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Method 1 – Counts / Aggregates

• Counts or aggregates - replicates

• Counts only - generalized

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Method 1 – Counts / Aggregates

• Some (but not all) years have GQs– M is total number of years

– N is the number of years with GQ data

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Method 1 – Counts / Aggregates

• Counts or aggregates – replicates

• Counts – generalized

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Method 1 – Counts Example

Estimate 2005 2006 2005-2006 Total

2005-2006 Period Est

HU Population 825,598 828,561 1,654,159 827,080

GQ Population NA 24,915 24,915 24,915

Males 403,999 413,539 414,921

Males in HUs 403,999 401,235 805,234 402,617

Males in GQs NA 12,304 12,304 12,304

Females 421,599 439,937 437,074

Females in HUs 421,599 427,326 848,925 424,463

Females in GQs NA 12,611 12,611 12,611

State of Delaware

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Method 1 – Ratios

• All years have GQs or only interested in HU or household pop

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Method 1 – Ratios

• Replicates

• Proportion/percents only - generalized

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Method 1 – Ratios

• Some (but not all) years have GQs– M is total number of years

– N is the number of years with GQ data

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Method 1 – Ratios

• Replicates

• Proportion/percents only - generalized

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Method 1 – Medians

• All years have GQs or only interested

in HU or household pop

• Normal median (X) on the combined

data

• Categorical median (Interpolated)

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Method 1 – Medians

• Replicates

• Generalized – Can be done

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Method 1 – Medians

• Some (but not all) years have GQs

• Use method 2

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Method 2

• Concatenate single year files

• Adjust weights

• Adjust dollar amounts for inflation

– Same approach as method 1

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Adjust Weights

• Adjustment factor is the number of years being combined

• Divide by the factorType of Record

2005-2006 Period 2005-2007 Period

2005 Factor

2006 Factor

2005 Factor

2006 Factor

2007 Factor

HU Person 2 2 3 3 3

GQ Person NA 1 NA 2 2

HU 2 2 3 3 3

GQ on HU NA NA NA NA NA

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Adjust Weights – Example 1

• 2005-2006 Estimate (PWGTP)

• 2005 HU person - weight 50 becomes 25

• 2006 HU person - weight 75 becomes 37.5

• 2006 GQ person - weight 60 will stay 60

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Adjust Weights – Example 2

• 2005-2007 Estimate (PWGTP)

• 2005 HU person - weight 67 becomes 22.333333

• 2006 HU person - weight 50 becomes 16.666667

• 2007 HU person - weight 75 becomes 25

• 2006 GQ person - weight 60 becomes 30

• 2007 GQ person - weight 55 becomes 27.5

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Contact Information

Anthony.G.Tersine.Jr@census.gov

Alfredo.Navarro@census.gov