Over the past year, I've noticed a topic where Less Wrong might have a blind spot: public opinion. Since last September I've had (or butted into) five conversations here where someone's written something which made me think, "you wouldn't be saying that if you'd looked up surveys where people were actually asked about this". The following list includes six findings I've brought up in those LW threads. All of the findings come from surveys of public opinion in the United States, though some of the results are so obvious that polls scarcely seem necessary to establish their truth.

1. The public's view of the harms and benefits from scientific research has consistently become more pessimistic since the National Science Foundation began its surveys in 1979. (In the wake of repeated misconduct scandals, and controversies like those over vaccination, global warming, fluoridation, animal research, stem cells, and genetic modification, people consider scientists less objective and less trustworthy.)
2. Most adults identify as neither Republican nor Democrat. (Although the public is far from apolitical, lots of people are unhappy with how politics currently works, and also recognize that their beliefs align imperfectly with the simplistic left-right axis. This dissuades them from identifying with mainstream parties.)
3. Adults under 30 are less likely to believe that abortion should be illegal than the middle-aged. (Younger adults tend to be more socially liberal in general than their parents' generation.)
4. In the 1960s, those under 30 were less likely than the middle-aged to think the US made a mistake in sending troops to fight in Vietnam. (The under-30s were more likely to be students and/or highly educated, and more educated people were less likely to think sending troops to Vietnam was a mistake.)
5. The Harris Survey asked, in November 1969, "as far as their objectives are concerned, do you sympathize with the goals of the people who are demonstrating, marching, and protesting against the war in Vietnam, or do you disagree with their goals?" Most respondents aged 50+ sympathized with the protesters' goals, whereas only 28% of under-35s did. (Despite the specific wording of the question, the younger respondents worried that the protests reflected badly on their demographic, whereas older respondents were more often glad to see their own dissent voiced.)
6. A 2002 survey found that about 90% of adult smokers agreed with the statement, "If you had to do it over again, you would not have started smoking." (While most smokers derive enjoyment from smoking, many weight smoking's negative consequences strongly enough that they'd rather not smoke; they continue smoking because of habit or addiction.)

If you've read Eliezer's "Hindsight Devalues Science", you're probably starting to feel déjà vu, and might have guessed that I'm bluffing you to make a point. If so, well done — you're quite correct! But before you assume I'm about to repeat Eliezer's trick and stop there, read the other half of my list:

1. The public's view of the harms and benefits from scientific research has remained about the same since the National Science Foundation began its surveys in 1979. (Despite the last 35 years of scientific scandals and controversies, people appreciate the technological advances science brings, and think scientists come off well compared to other professions.)
2. Most adults identify as Republican or Democrat. (Although many are dissatisfied with contemporary politics, most voters' political views are nonetheless represented better by one mainstream party than the other, and people find it logical to give more power to the party which supports more of one's preferred policies.)
3. Adults under 30 are more likely to believe that abortion should be illegal than the middle-aged. (Younger adults, being less reflective in general, tend to have more extreme political beliefs than the middle-aged.)
4. In the 1960s, those under 30 were more likely than the middle-aged to think the US made a mistake in sending troops to fight in Vietnam. (The under-30s were more likely to be students and/or highly educated, and more educated people were more likely to think sending troops to Vietnam was a mistake.)
5. The Harris Survey asked, in November 1969, "as far as their objectives are concerned, do you sympathize with the goals of the people who are demonstrating, marching, and protesting against the war in Vietnam, or do you disagree with their goals?" Most respondents aged 35 or less sympathized with the protesters' goals, whereas only 28% of those aged 50+ did. (Younger people were more anti-authoritarian, which translated to more sympathy for protesters regardless of their goals.)
6. A 2002 survey found that about 90% of adult smokers disagreed with the statement, "If you had to do it over again, you would not have started smoking." (Whatever the other consequences, smokers derive much pleasure from the experience of smoking, and even an addict who suffers major harm could justify their addiction as the result of a rational decision.)

Here's my twist on Eliezer's twist. It is technically true that the list includes six true findings, but the complete list has 12 items, so half of the statements are false. I made up the false statements as fake variations on the true findings, concocted parenthetical rationalizations for them, and randomly mixed the false claims with the true. I expect a lot of people reading this would, after seeing the full list, have a hard time sorting the true from the false without looking at the data — including the people who nodded along in agreement with the first half of the list.

Totally spurious beliefs about public opinion can have a ring of plausibility, especially because it's easy to invent sensible-sounding reasons why they ought to be correct. The availability heuristic presumably plays a role too, with people inferring the state of public opinion from what their friends & acquaintances think, not accounting for how unrepresentative their social network is. In any event, people's opinions of public opinion are often wrong, and it's worth taking a couple of minutes to look for Gallup poll results and the like online before commenting on public opinion.

Sources. On perceptions of whether the benefits of science outweigh its harmful results, see figure 7-11 from chapter 7 of the National Science Foundation's "Science and Engineering Indicators 2012". On party affiliation, see the polls Gallup runs every month. On abortion views, Pew Research Center has statistics for 2007 through 2012. For a breakdown of beliefs about the Vietnam War by age, consult Hazel Erskine's 1970 article "The Polls: Is War a Mistake?" (Public Opinion Quarterly, 34(1), 134–150); Jim Miller extends the data to May 1971, but presents them somewhat differently. On smokers' regrets, see Geoffrey T. Fong et al.'s 2004 article "The near-universal experience of regret among smokers in four countries: Findings from the International Tobacco Control Policy Evaluation Survey" (Nicotine & Tobacco Research, 6(S3), S341–S351). ↩