Global Methodology
Results for the 2021 life evaluation ratings are based on nationally representative, probability-based samples among the adult populations, aged 15 and older, in 116 countries and areas surveyed between April 2021 and January 2022. Surveys were conducted either through telephone or face-to-face interviews.
For results based on the total sample of national adults, the margin of sampling error ranges from ±2.8 to ±5.0 percentage points at the 95% confidence level.
The margin of error reflects the influence of data weighting. In addition to sampling error, question wording and practical difficulties in conducting surveys can introduce error or bias into the findings of public opinion polls.
U.S. Methodology
Results from the most recent survey, conducted Feb. 15-23, 2022, are based on responses from 2,837 adults, aged 18 and older, living in all 50 U.S. states and the District of Columbia as part of the Gallup Panel. For results based on this sample of national adults, the margin of sampling error is about ±2.3 percentage points at the 95% confidence level.
Most Gallup Panel monthly samples from February 2022 backward to August 2020 were between 2,500 and 4,000 respondents. Monthly samples from July 2020 backward to October 2019 were composed of 10,259; 10,779; 11,221; 16,584; 4,357; 9,155; 9,082; 20,006; 9,317; and 33,451 respondents, respectively.
Results from July 31 to Sept. 3, 2020, are based on a survey conducted by mail and web as part of the Gallup National Health and Well-Being Index, with a random sample of 2,321 adults, living in all 50 U.S. states and the District of Columbia.
Results from January 2018 through August 2019 are based on surveys conducted by mail and web as part of the Gallup National Health and Well-Being Index, with a random sample of 9,664 adults in 2019, living in all 50 U.S. states and the District of Columbia and another 115,929 in 2018. About 80% of all surveys completed in 2018 and 2019 were done so by mail.
Prior years of measurement were based on telephone interviews conducted daily from Jan. 2 to Dec. 30 of each year with roughly equally sized samples each month. In 2017, 2016, 2015 and 2014, a total of 161,161; 177,192; 177,281; and 176,702 interviews were completed, respectively. Each daily sample of national adults for data collected between Jan. 2, 2014, and Aug. 31, 2015, comprised 50% cellphone respondents and 50% landline respondents. Each daily sample from Sept. 1, 2015, to Dec. 30, 2016, comprised 60% cellphone respondents and 40% landline respondents. Daily samples in 2017 consisted of 70% cellphone respondents and 30% landline respondents. Additional minimum quotas by time zone and within region are included in the sampling approach.
Samples are weighted to correct for unequal selection probability, nonresponse, and double coverage of landline and cell users in the two sampling frames. They are also weighted to match the national demographics of gender, age, race, Hispanic ethnicity, education, region, population density and phone status (cellphone only/landline only/both and cellphone mostly). Demographic weighting targets are based on the March 2019 Current Population Survey figures for the aged 18 and older U.S. population. Population density targets are based on the 2010 census. All reported margins of sampling error include the computed design effects for weighting.
The means of data collection (e.g., mail/web versus phone) can result in differing estimates for some metrics in randomized large population polling. Gallup has extensively studied these effects and has determined that Life Evaluation (% thriving) is comparable across modes, thus effectively preserving past trending without the need for an adjustment due to the change in mode.
Comparisons of national weighted estimates from samples that fielded at similar time periods between Gallup’s National Panel of Households and the Gallup National Health and Well-Being Index demonstrated highly convergent results with statistically insignificant differences.