* La question était formulée par la source comme suit : «  Now, thinking personnally, to what extent do you agree or disagree with the following statement ? - I frequently give blood to help others. »

** La source ajoute les informations suivantes :
« • The survey comprising questions A1-A5 was conducted between April 20 and May 4, 2018 with 20,767 adults across 27 countries: Argentina, Australia, Belgium, Brazil, Canada, Chile, China, France, Great Britain, Germany, Hungary, India, Italy, Japan, Malaysia, Mexico, Peru, Poland, Russia, Saudi Arabia, Serbia, South Africa, South Korea, Spain, Sweden, Turkey and the United States.
• The survey comprising questions B1-B13 was conducted between May 25 and June 8, 2018 with 23,249 adults across 28 countries (the same as above plus Colombia).
• All survey respondents are aged 18-64 in Canada and the U.S. and 16-64 in all other countries.
• The sample size per country in each survey is approximately N=1,000 for Australia, Brazil, Canada, China, France, Italy, Japan, Malaysia, Spain, Germany, Great Britain, and the U.S., and approximately N=500 for Argentina, Belgium, Colombia, Chile,Hungary, India, Mexico, Peru, Poland, Russia, Saudi Arabia, Serbia, South Africa, South Korea, Sweden, and Turkey.
• Weighting has been employed to balance demographics and ensure that the sample’s composition reflects that of the adult population according to the most recent country census data.
• A survey with an unweighted probability sample of this size would have an estimated margin of error of +/- 3.1 percentage points for a sample of 1,000 and an estimated margin of error of +/- 4.5 percentage points for a 500 sample 19 times out of 20.
• In 17 of the countries surveyed ,internet penetration is sufficiently high to think of the samples as representative of the national population within the age ranges covered: Argentina, Australia, Belgium, Canada, France, Germany, Hungary, Italy, Japan, Poland, Serbia, South Korea, Spain, Sweden, Great Britain, and U.S. Brazil, Chile, China, Colombia, India, Malaysia, Mexico, Russia, Peru, Saudi Arabia, South Africa, and Turkey have lower levels of internet penetration. Samples from those countries should not be considered to be fully nationally representative, but instead torepresent a more affluent, connected population, representing an important and emerging middle class.
• Results may not always sum to 100 percent or may be 1 point higher/lower than the actuals due to rounding, multiple responses or the exclusion of don't knows or not stated responses. »