2025 National Public Opinion Reference Survey methodology
Summary
SSRS conducted the National Public Opinion Reference Survey (NPORS) for Pew Research Center using address-based sampling and a multimode protocol. The survey was fielded from Feb. 5, 2025, to June 18, 2025. Participants were first mailed an invitation to complete an online survey. A paper survey was later mailed to those who did not respond. Additionally, the mailings invited participants to call a toll-free number to take the survey over the phone with a live interviewer. In total, 2,349 respondents completed the survey online, 2,331 respondents completed the paper survey, and 342 respondents completed the survey over the phone (total n=5,022). The survey was administered in English and Spanish. The AAPOR Response Rate 1 was 29%.
Sample definition
The sample was drawn from the U.S. Postal Service Computerized Delivery Sequence File and was provided by MSG (Marketing Systems Group). Occupied residential addresses (including “drop points”) in all U.S. states (including Alaska and Hawaii) and the District of Columbia had a nonzero chance of selection. The draw was a national, stratified random sample, with differential probabilities of selection across the mutually exclusive strata. SSRS designed the sample plan as shown in the table above.
Mailing protocol
SSRS sent initial mailings in a 9-by-12-inch window envelope via first-class mail to the 18,800 sampled households. These packets included two $1 bills (visible from the outside of the envelope) and a letter that asked a member of the household to complete the survey. The letter provided a URL for the online survey; a toll-free call-in number; a password to enter on the online survey’s landing page, or tell the telephone interviewers if they chose to call in; and a FAQ section printed on the reverse side. If two or more adults were in the household, the letter asked the adult with the next birthday to complete the survey. Nonresponding households were later sent a reminder postcard and then a reminder letter via first-class mail.
After the web portion of the data collection period had ended, SSRS sent nonresponding households with a deliverable address a 9-by-12-inch Priority Mail window envelope. The Priority envelope contained a letter with a FAQ section printed on the reverse side, a visible $5 bill, a paper version of the survey and a postage-paid return envelope. The paper survey was one 11-by-17-inch page folded booklet-style. The within-household selection instructions were identical to those used in the earlier online survey request. The same households were later sent a second envelope containing another copy of the paper questionnaire by first-class mail.
The initial mailing was sent out in two separate launches: soft launch and full launch. The soft launch made up 5% of the sample and was sent out several days earlier than the full launch. The full launch consisted of the remaining sample.
Households in Hispanic-dominant census block groups received all materials in English and Spanish. All other households received materials in English only. Those who completed the survey online or returned the completed paper survey were sent a $10 post-paid incentive.
Questionnaire development and testing
Pew Research Center developed the questionnaire in consultation with SSRS. The online questionnaire was tested on both desktop and mobile devices. The test data was analyzed to ensure the logic and randomizations were working as intended before the survey was launched.
Weighting
The survey was weighted to support reliable inference from the sample to the target population of U.S. adults. The weight was created using a multistep process that includes a base weight adjusting for differential probabilities of selection and a raking calibration that aligns the survey with the population benchmarks. The process starts with the base weight, which accounted for the probability of selection of the address from the U.S. Postal Service Computerized Delivery Sequence File frame, as well as the number of adults living in the household, and incorporated an adaptive mode adjustment for cases that responded in an offline mode.
Then the base weights are calibrated to population benchmarks using raking, or iterative proportional fitting. The raking dimensions and the source for the population parameter estimates are reported in the table below. All raking targets are based on the noninstitutionalized U.S. adult population (ages 18 and older). These weights are trimmed at the 1st and 99th percentiles to reduce the loss in precision stemming from variance in the weights.
Design effect and margin of error
Weighting and survey design features that depart from simple random sampling tend to result in an increase in the variance of survey estimates. This increase, known as the design effect, or “deff,” should be incorporated into the margin of error, standard errors and tests of statistical significance. The overall design effect for a survey is commonly approximated as 1 plus the squared coefficient of variation of the weights.
For this survey, the margin of error (half-width of the 95% confidence interval) incorporating the design effect for full sample estimates at 50% is plus or minus 1.9 percentage points. Estimates based on subgroups will have larger margins of error. It is important to remember that random sampling error is only one possible source of error in a survey estimate. Other sources, such as question wording and reporting inaccuracy, may contribute additional error. A summary of the weights and their associated design effect is reported in the table below.
Dispositions
The table below reports the disposition of all sampled households for the survey.
2025 National Public Opinion Reference Survey sample sizes and margins of error
The following table shows the unweighted sample sizes and the error attributable to sampling that would be expected at the 95% level of confidence for different groups in the 2025 National Public Opinion Reference Survey (NPORS).
Sample sizes and sampling errors for other subgroups are available upon request. In addition to sampling error, one should bear in mind that question wording and practical difficulties in conducting surveys can introduce error or bias into the findings of opinion polls.
The American Trends Panel survey methodology
Overview
Data in this report comes from Wave 164 of the American Trends Panel (ATP), Pew Research Center’s nationally representative panel of randomly selected U.S. adults. The survey was conducted from Feb. 24 to March 2, 2025. A total of 5,123 panelists responded out of 5,737 who were sampled, for a survey-level response rate of 89%.
The cumulative response rate accounting for nonresponse to the recruitment surveys and attrition is 3%. The break-off rate among panelists who logged on to the survey and completed at least one item is 1%. The margin of sampling error for the full sample of 5,123 respondents is plus or minus 1.6 percentage points.
The survey includes an oversample of non-Hispanic Asian adults in order to provide more precise estimates of the opinions and experiences of these smaller demographic subgroups. These oversampled groups are weighted back to reflect their correct proportions in the population.
SSRS conducted the survey for Pew Research Center via online (n=4,939) and live telephone (n=184) interviewing. Interviews were conducted in both English and Spanish.
To learn more about the ATP, read “About the American Trends Panel.”
Panel recruitment
Since 2018, the ATP has used address-based sampling (ABS) for recruitment. A study cover letter and a pre-incentive are mailed to a stratified, random sample of households selected from the U.S. Postal Service’s Computerized Delivery Sequence File. This Postal Service file has been estimated to cover 90% to 98% of the population.2 Within each sampled household, the adult with the next birthday is selected to participate. Other details of the ABS recruitment protocol have changed over time but are available upon request.3 Prior to 2018, the ATP was recruited using landline and cellphone random-digit-dial surveys administered in English and Spanish.
A national sample of U.S. adults has been recruited to the ATP approximately once per year since 2014. In some years, the recruitment has included additional efforts (known as an “oversample”) to improve the accuracy of data for underrepresented groups. For example, Hispanic adults, Black adults and Asian adults were oversampled in 2019, 2022 and 2023, respectively.
Sample design
The overall target population for this survey was noninstitutionalized persons ages 18 and older living in the United States. It featured a stratified random sample from the ATP in which non-Hispanic Asian adults were selected with certainty. The remaining panelists were sampled at rates designed to ensure that the share of respondents in each stratum is proportional to its share of the U.S. adult population to the greatest extent possible. Respondent weights are adjusted to account for differential probabilities of selection as described in the Weighting section below.
Questionnaire development and testing
The questionnaire was developed by Pew Research Center in consultation with SSRS. The web program used for online respondents was rigorously tested on both PC and mobile devices by the SSRS project team and Pew Research Center researchers. The SSRS project team also populated test data that was analyzed in SPSS to ensure the logic and randomizations were working as intended before launching the survey.
Incentives
All respondents were offered a post-paid incentive for their participation. Respondents could choose to receive the post-paid incentive in the form of a check or gift code to Amazon.com, Target.com or Walmart.com. Incentive amounts ranged from $5 to $20 depending on whether the respondent belongs to a part of the population that is harder or easier to reach. Differential incentive amounts were designed to increase panel survey participation among groups that traditionally have low survey response propensities.
Data collection protocol
The data collection field period for this survey was Feb. 24 to March 2, 2025. Surveys were conducted via self-administered web survey or by live telephone interviewing.
For panelists who take surveys online: Postcard notifications were mailed to a subset on Feb. 24.4 Survey invitations were sent out in two separate launches: soft launch and full launch. Sixty panelists were included in the soft launch, which began with an initial invitation sent on Feb. 24. All remaining English- and Spanish-speaking sampled online panelists were included in the full launch and were sent an invitation on Feb 25.
Panelists participating online were sent an email invitation and up to two email reminders if they did not respond to the survey. ATP panelists who consented to SMS messages were sent an SMS invitation with a link to the survey and up to two SMS reminders.
For panelists who take surveys over the phone with a live interviewer: Prenotification postcards were mailed on Feb. 21, 2025. Soft launch took place on Feb. 24, 2025, and involved dialing until a total of three interviews had been completed. All remaining English- and Spanish-speaking sampled phone panelists’ numbers were dialed throughout the remaining field period. Panelists who take surveys via phone can receive up to six calls from trained SSRS interviewers.
Data quality checks
To ensure high-quality data, Center researchers performed data quality checks to identify any respondents showing patterns of satisficing. This includes checking for whether respondents left questions blank at very high rates or always selected the first or last answer presented. As a result of this checking, two ATP respondents were removed from the survey dataset prior to weighting and analysis.
Weighting
The ATP data is weighted in a process that accounts for multiple stages of sampling and nonresponse that occur at different points in the panel survey process. First, each panelist begins with a base weight that reflects their probability of recruitment into the panel. These weights are then calibrated to align with the population benchmarks in the accompanying table to correct for nonresponse to recruitment surveys and panel attrition. If only a subsample of panelists was invited to participate in the wave, this weight is adjusted to account for any differential probabilities of selection.
Among the panelists who completed the survey, this weight is then calibrated again to align with the population benchmarks identified in the accompanying table and trimmed at the 1st and 99th percentiles to reduce the loss in precision stemming from variance in the weights. Sampling errors and tests of statistical significance take into account the effect of weighting.
The following table shows the unweighted sample sizes and the error attributable to sampling that would be expected at the 95% level of confidence for different groups in the survey.
Sample sizes and sampling errors for other subgroups are available upon request. In addition to sampling error, one should bear in mind that question wording and practical difficulties in conducting surveys can introduce error or bias into the findings of opinion polls.
Dispositions and response rates
How family income tiers are calculated
Family income data reported in this study is adjusted for household size and cost-of-living differences by geography. Panelists then are assigned to income tiers that are based on the median adjusted family income of all American Trends Panel members. The process uses the following steps:
- First, panelists are assigned to the midpoint of the income range they selected in a family income question that was measured on either the most recent annual profile survey or, for newly recruited panelists, their recruitment survey. This provides an approximate income value that can be used in calculations for the adjustment.
- Next, these income values are adjusted for the cost of living in the geographic area where the panelist lives. This is calculated using price indexes published by the U.S. Bureau of Economic Analysis. These indexes, known as Regional Price Parities (RPP), compare the prices of goods and services across all U.S. metropolitan statistical areas as well as non-metro areas with the national average prices for the same goods and services. The most recent available data at the time of the annual profile survey is from 2022. Those who fall outside of metropolitan statistical areas are assigned the overall RPP for their state’s non-metropolitan area.
- Family incomes are further adjusted for the number of people in a household using the methodology from Pew Research Center’s previous work on the American middle class. This is done because a four-person household with an income of say, $50,000, faces a tighter budget constraint than a two-person household with the same income.
- Panelists are then assigned an income tier. “Middle-income” adults are in families with adjusted family incomes that are between two-thirds and double the median adjusted family income for the full ATP at the time of the most recent annual profile survey. The median adjusted family income for the panel is roughly $74,100. Using this median income, the middle-income range is about $49,400 to $148,200. Lower-income families have adjusted incomes less than $49,400 and upper-income families have adjusted incomes greater than $148,200 (all figures expressed in 2023 dollars and scaled to a household size of three). If a panelist did not provide their income and/or their household size, they are assigned “no answer” in the income tier variable.
Two examples of how a given area’s cost-of-living adjustment was calculated are as follows: the Pine Bluff metropolitan area in Arkansas is a relatively inexpensive area, with a price level that is 19.1% less than the national average. The San Francisco-Oakland-Berkeley metropolitan area in California is one of the most expensive areas, with a price level that is 17.9% higher than the national average. Income in the sample is adjusted to make up for this difference. As a result, a family with an income of $40,400 in the Pine Bluff area is as well off financially as a family of the same size with an income of $58,900 in San Francisco.
