Results are based on telephone and face-to-face interviews with 453,122 adults, aged 15 and older, in 152 countries from 2015 to 2017. The 152 countries surveyed represent about 99% of the world's adult population. For most countries, aggregated sample sizes (across multiple years of surveys) range between 1,000 and 4,000 interviews. As with any survey-based estimate, the indexes reported in this article have corresponding margins of error, calculated using the Standard Error of the index. Sample size, size of the country and range in population projection weights affect margin of error of the indexes.
All scores are relative to a country’s population size, and this should be kept in mind when interpreting results. For example, the PNMI for the U.S. is estimated at +46%, meaning if all adults who desire to move in and out of the country did so, the adult population would increase by 46%. With the margin of error at the 95% confidence level, this estimate ranges from 50% to 42%.
PNMI scores are not reported for countries with a total sample size of less than 500 because of the volatility in the index as measured by the margin of error. Potential Net Brain Gain and Potential Net Youth Migration indexes are not reported for countries with a sample size of less than 200.
The PNMI is measured on a scale of -100 (meaning the total adult population of the country would leave) to infinity (meaning the potential inflow of adult population to the country is unlimited and depends on the number of adults who want to move in from around the world).
The Potential Net Brain Gain Index is measured on a scale of -100% (meaning the total population of highly educated residents -- those who have completed four years of education beyond high school or have the equivalent of a bachelor's degree -- would leave) to infinity (meaning the potential inflow of this highly educated group is unlimited and depends on the number who want to move in from around the world).
The Potential Net Youth Migration Index is measured on a scale of -100% (meaning the total aged 15-to-29 population of the country would leave) to infinity (meaning the potential inflow of 15- to 29-year-olds is unlimited and depends on the number who want to move in from around the world).
Gallup's migration indexes are based on responses to the following questions:
- Ideally, if you had the opportunity, would you like to move permanently to another country, or would you prefer to continue living in this country?
- (If "would like to move permanently to another country") To which country would you like to move? [Open-ended, one response allowed]
