In the past year or so, there have been at least four major American opinion polls on evolution, and they’ve given wildly divergent results, and even different trends in levels of support for Darwin’s theory of evolution. Are the sampling techniques faulty, or are the surveys sloppily worded?
The recent American opinion polls on evolution which I’ve identified are as follows:
Gallup poll, May 3-6, 2012
Pew Research Center poll, March 21-April 8, 2013
Yougov Omnibus poll, July 8-9, 2013
Harris Interactive poll, November 13-18, 2013
Before I discuss the strengths and weaknesses of these surveys, I’d like to summarize their findings.
Survey Results
1. Gallup poll, May 3-6, 2012:
“Which of the following statements comes closest to your views on the origin and development of human beings?”
(a) Human beings have developed over millions of years from less advanced forms of life, but God had no part in this process: 15% (14% in 2008, 16% in 2010)
Breakdown:
Republican 5%, Independent 19%, Democrat 19%.
High school or less 11%, some college 13%, college graduate 14%, postgraduate 29%.
(b) Human beings have developed over millions of years from less advanced forms of life, but God guided this process: 32% (down from 36% in 2008 and 38% in 2010)
Breakdown:
Republicans 31%, Independents 34%, Democrats 32%.
High school or less 25%, some college 36%, college graduate 35%, postgraduate 42%.
(c) God created human beings pretty much in their present form at one time within the last 10,000 years or so: 46% (44% in 2008, 40% in 2010)
Breakdown:
Republican 58%, Independent 39%, Democrat 41%.
High school or less 52%, some college 47%, college graduate 46%, postgraduate 25%.
(d) Not sure: 7% (6% in 2008, 6% in 2010).
2. Pew Research Center poll, March 21-April 8, 2013:
“Which comes closer to your view?”
Humans and other living things have evolved due to natural processes such as natural selection: 32% (32% in 2009)
A supreme being guided the evolution of living things for the purpose of creating humans and other life in the form it exists: 24% (22% in 2009)
Humans and other living things have evolved over time, couldn’t say how: 4% (7% in 2009)
Total (Humans and other living things have evolved over time): 60% (61% in 2009)
Breakdown:
Men 65%, women 55%.
Aged 18-29 68%, 30-49 60%, 50-64 59%, 65+ 49%.
High school or less 51%, some college 62%, college grad+ 72%.
Republicans 43%, Independents 65%, Democrats 67%.
Humans and other living things have existed in their present form since the beginning of time: 33% (31% in 2009)
Breakdown:
Men 28%, women 38%.
Aged 18-29 27%, 30-49 33%, 50-64 35%, 65+ 36%.
High school or less 38%, some college 33%, college grad+ 24%.
Republicans 48%, Independents 28%, Democrats 27%.
Don’t know/Refused to answer: 7% (8% in 2009)
3. Yougov Omnibus poll, July 8-9, 2013:
“Which of the following statements comes closest to your views on the origin of human beings?”
Human beings evolved from less advanced life forms over millions of years, and God did not directly guide this process: 21%
Breakdown:
Men 26%, Women 17%.
Aged 18-29 31%, 30-44 21%, 45-64 17%, 65+ 20%.
Republican 5%, Independent 26%, Democrat 28%.
Human begins evolved from less advanced life forms over millions of years, but God guided this process: 25%
Breakdown:
Men 30%, Women 20%.
Aged 18-29 29%, 30-44 19%, 45-64 27%, 65+ 23%.
Republican 30%, Independent 21%, Democrat 25%.
God created human beings in their present form within the last ten thousand years: 37%
Breakdown:
Men 31%, Women 43%.
Aged 18-29 21%, 30-44 43%, 45-64 42%, 65+ 39%.
Republican 55%, Independent 32%, Democrat 31%.
Not sure: 17%
Breakdown:
Men 13%, Women 14%.
Aged 18-29 19%, 30-44 17%, 45-64 14%, 65+ 18%.
Republican 10%, Independent 21%, Democrat 16%.
4. Harris Interactive poll, November 13-18, 2013:
“Please indicate for each one if you believe in it, or not”
Darwin’s theory of evolution: 47% (29% don’t believe, 25% aren’t sure). In 2007, 42% believed in Darwin’s theory, while in 2009, 45% did.
Breakdown:
Aged 18-36 49%, 37-48 48%, 49-67 45%, 68+ 43%.
Republican 36%, Independent 51%, Democrat 52%.
Creationism: 36% (31% don’t believe, 33% aren’t sure). In 2007, 39% believed in Darwin’s theory, while in 2009, 40% did.
Breakdown:
Aged 18-36 33%, 37-48 35%, 49-67 38%, 68+ 37%.
Republican 49%, Independent 34%, Democrat 30%.
Comparison of the survey results
According to the Gallup poll, only 15% of Americans agree with the statement, “Human beings have developed over millions of years from less advanced forms of life, but God had no part in this process.” According to the Pew Research Center poll, 32% of Americans believe that “humans and other living things have evolved due to natural processes such as natural selection,” as opposed to a supreme being guiding the evolution of living things. According to the Yougov Omnibus poll, 21% of Americans agree with the statement, “Human beings evolved from less advanced life forms over millions of years, and God did not directly guide this process.” And according to the Harris Interactive poll, 47% of Americans believe in “Darwin’s theory of evolution.”
What’s going on here? First of all, only the Gallup poll question expressly stipulated that “God had no part in this process.” The Pew Research Center poll was somewhat less clear, stipulating that humans had evolved “due to natural processes,” as opposed to God-guided processes. Still, it’s possible that some “Yes” answers to this question came from people who believe God deliberately set up natural processes to generate human beings and other life-forms, without the need for any guidance. The Yougov Omnibus poll question was even vaguer, saying only that “God did not directly guide this process.” An affirmative answer to this question might mean that the respondent did not believe in God, or that they believed in God but thought He didn’t guide evolution at all, or that they believed in God but thought He indirectly guided evolution. Finally, the Harris Interactive poll referred to “Darwin’s theory of evolution,” without indicating whether it was God-guided or a purely naturalistic.
My conclusion is that we’re talking about an apples-and-oranges comparison between the different polls, here. Still, the large difference between the Gallup poll (in which 15% of Americans say that human beings have developed from less advanced life-forms, but “God had no part in this process”) and the Pew Research Center poll (in which 32% say that “humans and other living things have evolved due to natural processes such as natural selection”) is worrying. It appears that slight changes in wording can produce drastically different results.
According to the Gallup poll, 46% of Americans believe that “God created human beings pretty much in their present form at one time within the last 10,000 years or so,” while in the Pew Research Center poll, only 33% believe that “Humans and other living things have existed in their present form since the beginning of time.” Someone is clearly wrong here. Who is it? According to the Yougov Omnibus survey, 37% of Americans believe that “God created human beings in their present form within the last ten thousand years,” while according to the Harris Interactive poll, 36% believe in creationism (compared with 47% for Darwin’s theory of natural selection).
Clearly the Gallup poll is the outlier here. The true proportion of creationists in the American population is probably somewhere between 33 and 37%.
Speaking of creationists, I notice that none of the surveys asked people about old-earth creationism. What about people who believe that God created human beings in their present form 200,000 years ago (at the dawn of Homo sapiens)? Or what about people who believe that God created human beings in a slightly different form around 1,000,000 years ago (Heidelberg man, the presumed ancestor of Homo sapiens, Neandertal man and Denisovan man)?
There was a greater degree of agreement between the different polls on public acceptance of God-guided evolution: 32% (Gallup), 24% (Pew Research Center) and 25% (Yougov).
The polls also gave diverging answers to the question of whether popular support for evolution is rising or falling: according to Gallup, support for theistic evolution is down, while support for creationism is up, with little or no change in the level of support for atheistic evolution; according to the Pew Research Center, support for creationism is up slightly while support for evolution is down very slightly; and according to the Harris Interactive poll, support for Darwinism is up, while support for creationism is down. Who’s right? Personally, I doubt very much that the level of support for creationism really increased from 40% to 46% between 2010 and 2012, as the Gallup survey indicated. That sounds much more like a sampling error to me. I think it’s more likely that the level of support for Darwinism has risen, if anything, given the current political climate – but I can’t prove that.
However, the surveys did agree on one clearly discernible trend: considerably more young people than old people believe in evolution. Is this a sign of things to come? I wonder.
Interestingly, the percentage of people who weren’t sure about human origins varied enormously between the different polls, from 7% in the Gallup and Pew Research Center polls to 17% in the Yougov poll to 25% who were unsure about Darwin’s theory and 33% who were unsure about creationism in the Harris Interactive poll. It seems that if you ask people, “Do you believe in X or Y?” instead of asking “Do you believe in X?” and then “Do you believe in Y?”, you get fewer “Don’t knows.”
Do Americans hold inconsistent attitudes?
In 2008, a Harris Interactive survey collected data regarding Americans’ knowledge of and beliefs about evolution. There were 4626 respondents, in two waves of data collection from July to October, 2009. Respondents were selected from Harris Interactive’s on-line panel and weighted based on age, sex, region of country, income, education, and ethnicity, to reflect the proportions of these various groups in the US Census. The survey, which the National Council for Science Education carried a report on, came up with some bizarre and contradictory findings.
An old Earth
Layers of rock containing fossils cover the earth’s surface and date back hundreds of millions of years (78%).
Dinosaurs became extinct about 65 million years ago (69%).
All life forms are descended from common ancestors that developed over millions of years (65%).
Birds appear to have evolved from dinosaurs (55%).
Living organisms on earth have evolved over a billion years ago from nonliving chemicals (44%).
The earth is less than 10,000 years old. (18%)
God-guided evolution
God started the evolutionary process and directed it over millions of years (56%).
God has intervened in the evolutionary process to create millions of species at various times over millions of years (54%).
Humans are so complex, advanced, and unique that we cannot have arisen due to chance events (60%).
All people are descendants of one man and one woman — Adam and Eve (60%).
Six-day creation
The Bible describes the creation of life exactly as it occurred in six days (50%).
Human fossils have been found mixed in with dinosaur fossils showing that humans existed at the same time that dinosaurs existed (43%).
God created the universe, the earth, the sun, moon, stars, plants, animals, and the first two people within the past 10,000 years (39%).
A recent flood
There was a flood within the past 10,000 years that covered all of the earth and was responsible for most of the rock layers and fossils that are seen across the world (60%).
How can we resolve these seemingly contradictory beliefs? First, I’d suggest that the true level of support for a young Earth is probably under 20%, given that only 18% agreed with the statement, “The earth is less than 10,000 years old,” and that 79% agreed with the statement, “Layers of rock containing fossils cover the earth’s surface and date back hundreds of millions of years.” Many of the 50% who agreed that “The Bible describes the creation of life exactly as it occurred in six days” might have envisaged the days as periods of time, while the 39% level of agreement with the statement, “God created the universe, the earth, the sun, moon, stars, plants, animals, and the first two people within the past 10,000 years,” can be explained by people honing in on the last part of the statement: “the first two people within the past 10,000 years.” Given that we concluded earlier that 33 to 37% of Americans are creationists, it’s highly likely that something like 39% think the human race is 10,000 years old or less, while the astonishingly high 43% of Americans who think that humans and dinosaurs co-existed may include not only young earth creationists, but also (a) people who think that dinosaurs first appeared millions of years ago but were still alive 10,000 years ago, or (b) people who mistakenly think that the human race is tens of millions of years old, which is far older than scientists think it is!
Belief in Adam and Eve still appears to be widespread (60%). But I’d say that a sizable proportion of these 60% are either old Earth creationists or theistic evolutionists who believe that God guided evolution over millions of years and at some point in time, infused a spiritual soul into two chosen hominins. Belief in an Adam and Eve who were created within the last 10,000 years is probably just below 40%, given that 39% of people surveyed accepted the statement that God created “the first two people within the past 10,000 years.”
Belief in a global Flood that deposited many fossils within the last 10,000 years is widespread among Americans (60%), but this belief is still logically compatible with the belief that the Earth that the Earth is millions of years old, and that at least some of the fossils we observe may predate the Flood.
I realize that people do hold inconsistent beliefs, and I don’t want to be accused of trying to square the circle, but I also believe that most people aren’t stupid. Hence when I see a glaring contradiction, I look for a reason that might explain it. The picture I get is that a large number of Americans believe in a mixed picture of the Earth’s geological history: they believe it has been shaped both by natural events over millions of years and by events described in the Bible, over the last few thousand years.
Sampling techniques and methodologies
Looking through the survey methodologies, which are described below, several things leaped out at me.
First, I noticed that the Yougov poll was not reflective of the general population, as can be seen from its FAQ page. Only Yougov members are surveyed, and they are offered a bonus to encourage them to participate in surveys: “YouGov polls are taken by people, from all over the nation, who have agreed to share their thoughts on a wide variety of important issues… When you take surveys you accumulate points which can later be redeemed for rewards.” I think we can safely disregard Yougov’s figures, even if their surveys may say something useful on broad social trends.
Second, I saw an awful lot of “data weighting” going on in the varius surveys, to reflect the proportions of various ethnic and income groups within the U.S. population. This kind of thing makes me suspicious. I can see the statistical rationale for it, but I do think that it would be nice, just for once, to see the “polished” survey results alongside the raw data, so that readers could judge for themselves whether the final results were generated in a fair and balanced fashion.
Third, I noticed a striking philosophical between Harris Interactive polls on the one hand, and Gallup and Pew Research Center polls, on the other. Harris Interactive polls believes that telephone surveys aren’t reliable and prefers to use the Internet (as does Yougov), while Gallup and Pew Research continue to rely on telephone polls. Why? Harris argues that “research has shown that when replying to a question administered impersonally by a computer, people are less likely to say they believe in God, or attend Church services when they really don’t,” whereas “surveys conducted by live interviewers tend to exaggerate the numbers of people who report the socially desirable, or less embarrassing, behavior.” Hence, they conclude, “the replies given to an online survey such as this, are more honest and therefore more accurate.” That’s a good point.
Harris weights its online survey results by age, sex, race/ethnicity, education, region and household income, to reflect the general population, but refuses to estimate a margin of error for its surveys as there are “multiple sources of error which are most often not possible to quantify or estimate.” Well, at least they’re honest and upfront about that.
My tentative conclusion, then, is that Harris’ methodology may be best suited to gauging people’s attitudes on sensitive topics. It is a pity, then, that their questions on creation and evolution were so broad: do you believe in Darwin’s theory of evolution or not? Do you believe in creationism or not? I hope that Harris Interactive will come up with a more “fine-grained” set of survey questions in the future.
Anyway, I invite readers to peruse the methodologies of the four surveys listed above, and draw their own conclusions.
1. Gallup poll, May 3-6, 2012:
“Results for this USA Today/Gallup poll are based on telephone interviews conducted May 10-13, 2012, with a random sample of 1,012 adults, aged 18 and older, living in all 50 U.S. states and the District of Columbia.
“For results based on the total sample of national adults, one can say with 95% confidence that the maximum margin of sampling error is ±4 percentage points.
“Interviews are conducted with respondents on landline telephones and cellular phones, with interviews conducted in Spanish for respondents who are primarily Spanish-speaking. Each sample includes a minimum quota of 400 cell phone respondents and 600 landline respondents per 1,000 national adults, with additional minimum quotas among landline respondents by region. Landline telephone numbers are chosen at random among listed telephone numbers. Cell phone numbers are selected using random-digit-dial methods. Landline respondents are chosen at random within each household on the basis of which member had the most recent birthday.
“Samples are weighted by gender, age, race, Hispanic ethnicity, education, region, adults in the household, and phone status (cell phone only/landline only/both, cell phone mostly, and having an unlisted landline number). Demographic weighting targets are based on the March 2011 Current Population Survey figures for the aged 18 and older non-institutionalized population living in U.S. telephone households.”
2. Pew Research Center poll, March 21-April 8, 2013
“This report is based on telephone interviews conducted March 21-April 8, 2013, among a national sample of 1,983 adults, 18 years of age or older, living in all 50 U.S. states and the District of Columbia (1,017 respondents were interviewed on a landline telephone, and 966 were interviewed on a cellphone). Interviews were completed in English and Spanish by live, professionally trained interviewing staff under the direction of Princeton Survey Research Associates International.
“A combination of landline and cell random digit dial (RDD) samples were used to reach a representative sample of all adults in the United States who have access to either a landline or cellphone. Both samples were disproportionately stratified to increase the incidence of African-American and Hispanic respondents. Within each stratum, phone numbers were drawn with equal probabilities. The landline samples were list-assisted and drawn from active blocks containing three or more residential listings, while the cell samples were not list-assisted but were drawn through a systematic sampling from dedicated wireless 100-blocks and shared service 100-blocks with no directory-listed landline numbers. Both the landline and cell RDD samples were disproportionately stratified by county based on estimated incidences of African-American and Hispanic respondents.
“Several stages of statistical adjustment or weighting are used to account for the complex nature of the sample design. The weights account for numerous factors, including (1) the different, disproportionate probabilities of selection in each stratum, (2) the overlap of the landline and cell RDD sample frames, and (3) differential non-response associated with sample demographics. Statistical results are weighted to correct known demographic discrepancies, including disproportionate stratification of the sample.
“The survey’s margin of error is the largest 95% confidence interval for any estimated proportion based on the total sample – the one around 50%. For example, the margin of error for the entire sample is +/-3.0 percentage points.
“Most analysis in this report is based on respondents asked about human evolution (N=1,983). An additional 2,023 respondents were asked questions about animal evolution. The margin of error for those asked about animal evolution is +/- 2.9 percentage points.”
3. Yougov Omnibus poll, July 8-9, 2013
“Evidently the sample size was 1000 and the survey was conducted July 8-9, 2013; further details of how the poll was conducted are not readily apparent.” (NCSE)
“YouGov conducts polls on the Internet about politics, public affairs, products, brands and other topics of general interest. YouGov polls are taken by people, from all over the nation, who have agreed to share their thoughts on a wide variety of important issues.” (Yougov Website, FAQ page.)
4. Harris Interactive poll, November 13-18, 2013
“Other research has shown that when replying to a question administered impersonally by a computer, people are less likely to say they believe in God, or attend Church services when they really don’t. It is generally believed that surveys conducted by live interviewers tend to exaggerate the numbers of people who report the socially desirable, or less embarrassing, behavior, and that the replies given to an online survey such as this, are more honest and therefore more accurate.
“This Harris Poll was conducted online within the United States November 13 and 18, 2013 among 2,250 adults (aged 18 and over). Figures for age, sex, race/ethnicity, education, region and household income were weighted where necessary to bring them into line with their actual proportions in the population. Propensity score weighting was also used to adjust for respondents’ propensity to be online.
“All sample surveys and polls, whether or not they use probability sampling, are subject to multiple sources of error which are most often not possible to quantify or estimate, including sampling error, coverage error, error associated with nonresponse, error associated with question wording and response options, and post-survey weighting and adjustments. Therefore, Harris Interactive avoids the words “margin of error” as they are misleading. All that can be calculated are different possible sampling errors with different probabilities for pure, unweighted, random samples with 100% response rates. These are only theoretical because no published polls come close to this ideal.
“Respondents for this survey were selected from among those who have agreed to participate in Harris Interactive surveys. The data have been weighted to reflect the composition of the adult population. Because the sample is based on those who agreed to participate in the Harris Interactive panel, no estimates of theoretical sampling error can be calculated.”
Well, that’s it, folks. Which survey do you trust the most, and why? And where do you see America heading, in the future?