Starting in January 2023, data users may note some changes to the Current Population Survey (CPS) public use files (PUF) designed to provide added confidentiality protection to these data. For an overview and background on these changes, please see https://www.census.gov/programs-surveys/cps/technical-documentation/user-notes/2023-cps-puf-changes.html. 

This User Note provides additional detail about these changes and addresses considerations that data users may have when using the data.

The changes will be phased in on a monthly basis. This means that in January 2023 only Month-in-Sample (MIS) 1 will reflect the changes. This phase-in will continue for 16 months until April 2024, at which time all cases on the CPS microdata files will reflect the revisions listed below.  This phase-in procedure will allow users to continue to conduct longitudinal analyses without having a break in series.

Starting in January 2023, all MIS 1 cases will be assigned Household Identification Numbers (HRHHID1) using an algorithm different than the one used in the current files.  As with the current files, these numbers will remain constant over the time that a household remains in sample such that users will be able to use the same matching identification for the life of the case.  This, along with HRHHID2, will uniquely identify a household.  This is for your information and the data user will not have to do anything different than in previous data use.

Section A:  Geographic Synthesis

All Geography with population between 100,000 and 249,999 will go through a geographic synthesis for privacy protection.  Items for consideration include the following:

1. The 2010 Census population measures were used for identifying areas with a population between 100,000 and 249,999.
2. There will be no revision to the current practice of geographic suppression of the data for populations under 100,000.
3. This synthesis will apply to all CBSAs, identified principal cities, counties, and the component parts of the CBSA (principal city and balance portions).  Additionally, CBSAs that cross state boundaries will be subject to synthesis separately for each state in which they occur.  The following are eligible for synthesis: 

a. GTCBSA


b. GTCBSAST


c. GTCBSASZ


d. GTCO


e. GTINDVPC


f. GTMETSTA


g. GTCSA


4. No other data are synthesized by the swap.

Determining which cases are eligible for synthesis

The following are key things to consider when looking at data that maybe eligible for geographic synthesis:

• While a specific geography may meet the population threshold for synthesis, not all cases in that geography will be synthesized. Some will not get synthesized and others will be synthesized back into their original geography.
• Both nonmetropolitan and metropolitan areas will be subject to synthesis.
• If a case is synthesized, all substate geographic codes will be updated to reflect the new geography.
• All the substate codes for areas synthesized are revised as a group such that there are no records with missing or inconsistent codes.

For example, the Salisbury CBSA is contained within the states of Maryland and Delaware, with each state-specific portion of the CBSA having a population of 100,000 to 249,999.  Thus, each state portion will be subject to the synthesis.  Conversely, the Wisconsin portion of the Minneapolis CBSA is subject to synthesis, but not the Minnesota portion since its population is over 249,999.  Additionally, there are some CBSAs only partially in sample. For these areas, the population for the portion of the area in sample will be used to determine whether it requires synthesis. 

What follows below are examples based on user questions and comments that arose as the Census Bureau vetted these changes to the CPS PUF over the course of the last year. We hope that these examples help to understand the scope of these changes more clearly.

• Let's take Delaware as an example.  There are 3 counties in the state, all of which are classified as metropolitan on the files. The county containing Wilmington (New Castle County, part of the Philadelphia CBSA in Delaware) has a population greater than 249,999 and will not be subject to synthesis.  The other 2 counties (Kent County, in the Dover CBSA; and Sussex County, part of the Salisbury CBSA in Delaware), each have a population between 100,000 and 249,999 and will both be subject to synthesis.  For these areas, the CBSA code and other geographic codes will change from Dover to Salisbury and vice versa for some cases while others will keep the original CBSA codes.
• We only had one state, Vermont, where there was a single area requiring synthesis.  In this case, we synthesized some of the nonmetropolitan areas along with synthesizing the Burlington CBSA.
• Another set of examples can be found in Arkansas. Here we will not synthesize any cases in either the Little Rock or Fayetteville CBSAs.  They will retain their original codes.  All the other areas in the state will be subject to synthesis and will either retain their original codes or the codes that were assigned by the synthesis process.

Analysis

Analysts at the Census Bureau reviewed 3 non-consecutive months of basic monthly public use data files to examine potential issues with the synthesized geographies. (As always, the Census Bureau urges caution when analyzing small sample sizes or subpopulations. For example, Census guidance recommends pooling three years of CPS ASEC to produce state-level estimates.)

Analysts examined demographics (age, marital status, sex, race, ethnicity, cohabitation status, household type) and key migration variables for differences in distributions between public use basic monthly files with and without geographic synthesis techniques applied. Additionally, analysts examined how geographic synthesis may affect the relationship between full-time employment status at the household level and household-level regressors, such as family income, race and ethnicity, education, average age, household tenure, employment status, disability, citizenship, marital status, having children, and veteran status. Analysts found no meaningful differences in distributions across the two sets of files, nor was there considerable evidence that the geographic synthesis changed the relationship between employment status and the examined variables.

One area of potential concern raised by external data users was the impact on the Supplemental Poverty Measure (SPM), which has geographically-adjusted thresholds. Census publications will continue to utilize the internal CPS ASEC files and therefore will be unaffected by changes in the CPS PUF. Nonetheless, estimates derived from the public use files were examined to see potential impacts on external data users. For the available subset of the 2022 CPS ASEC, SPM thresholds were re-calculated using synthesized geographies and used to re-estimate SPM rates overall and for detailed demographic subgroups (age, race and Hispanic origin, and CBSA status). The overall SPM rate was not statistically different when using geographically synthesized thresholds. However, significant differences were found with some demographic subgroups and regions, indicating the need for additional research once the geographic synthesis has been fully implemented. Differences in the distribution of people by income-to-poverty thresholds did not significantly change when estimating supplemental poverty using the new synthesized geographies. This remained true when looking at subsamples by CBSA status. 

As part of commitment to data users, Census will review the impacts on the current production data and release occasional reports on any possible impacts on data quality.  Census is constantly reviewing new methods for privacy protections and will refine the model should a better method be found that may lessen any impacts.

Section B – Changes to Earnings

Note: All changes in this section will not appear until April 2023 when MIS 4 cases are first phased in.

Rounding of the Usual Weekly Earnings Data

Provided below are the rounding algorithms that will be introduced for the implementation of rounding for the CPS files.   Table 1 is the rounding rules for the following hourly earning variables: PTERNHLY, PTERNH1O, PTERNH2, and PTERNH1C.  Table 2 is the rounding for the weekly earnings variables: PTERNWA, PTERN, and PTERN2.   Both variables still have the two implied decimals. 

Hourly Rounding Examples

For example, a value of $4.31/hour rounds down to a value of $4.30.  A value of $4.78/hour rounds up to a value of $4.80. 

A value of $8.22/hour rounds down to $8.20, while a value of $8.28/hour rounds up to $8.30. 

A value of $32.07/hour rounds down to $32.00 while a value of $32.64/hour rounds up to $32.75.

Weekly Rounding Examples

For example, a value of $217/week rounds up $218, while a value of $228.34/week rounds down to $228.00.

A value of $3,622.50/week rounds down to $3,620.00, while a value $3,653.00/week rounds up to $3,660.00.

Topcoding of Usual Weekly Earnings

Prior to this point in time, the CPS used a static topcode for these items that did not change month to month.  Currently, that value has been topcoding about 4 -5 percent of the values in these fields, while the Census Bureau’s requirement is the top 3 percent.  A dynamic topcode of 3 percent will be set each month moving forward.

As part of the new topcoding, the topcode will be calculated as a weighted average for all cases subject to the topcode.   By making this change, users will now have the ability to calculate accurate estimates for the aggregate combined earnings for all the records in sample. As topcodes may vary from month-to-month, care should be used when estimating average aggregate values over two or more months. It is suggested that a user works with the lowest topcode for the months under review to guarantee that all values greater than the smallest topcode are accounted for.

New Flag – PRERNMIN

In order to identify wages that were originally reported below the Federal Minimum wage even with rounding on the PUF, all records originally reported below 725 ($7.25) hourly will be flagged.  PRERNMIN is set to 1 if below minimum wage was reported.  PRERMIN can be found on the PUF in position 536-537.

For questions on technical issues involving these revisions, contact the CPS staff at:  301-763-3806 or email at DSD.CPS@census.gov