One of the ideas I’ve seen cropping up on social media and inmedia punditry(especially since 2016) is that polls are untrustworthy. The thinking goes like this:the polls predicted that Hillary Clinton would win; she didn’t; so polls must be useless (or at least no longer useful) when it comes to making political predictions.

这种对民意调查的怀疑有时表现出真诚的态度，但也经常表现出讥讽的态度，仿佛在说:“你这个傻瓜!You usepollingdata. Ha!” The general idea is that we live in an age in which people are so cynical that people’s answers to pollsters no longer reflect how they’re likely to vote.

Such thinking is worth addressing head on. It seems to me to be part of a broader assault on objective, systematic research that has also been on the rise since 2016. That assault—insofar as it undermines trust in real journalism and research—paves the way for propaganda, conspiracy theories, and other politically pernicious narratives, which thrive in ignorance. So the assault should be countered as much as possible.

My general stance, which is fairly standard among people who think at all seriously about polls, is that they are useful information sources under certain conditions. What are those conditions?

1. The polls are conducted by a legitimate polling or news organization, one with trained pollsters and journalists who try as hard as possible to get a representative sample. (It is, of course, possible to do biased polling by targeting a biased sample, but that doesn’t undermine the credibility of polling done well.)
2. They are consideredin the context of other polls on the same topic within the relevant time period. (Polls are just a small slice of the broader population, so one’s getting an unrepresentative sample by accident is common enough. In other words, don’t leap up and down about one poll and ignore the others; that’s a recipe for self-deception—and for being shocked when the single poll you read comes out “wrong.”)
3. They are used to answer the exact question for which they are intended. (The discussion below will make clear what this means.)

2016年的美国大选是否削弱了这一立场?

No, it doesn’t. The claim that it does rests failing to respect condition 3). Hillary Clinton was leading in national poll averages by about 2-4% on the eve of the election. So the fact that she lost theelectoral collegedoes not show that the national polls were useless. All it shows is something we knew all along: one can win the popular vote without winning the electoral college. If we respect condition 3) and use the national polls for the question for which they were intended (who will win the popular vote?), we see that they predicted things fairly well:Clinton received 48.5% of the popular vote; Trump received 46.4%. So national polls predicted what they were supposed to predict, namely, the popular vote. (It is fair to say, I grant, that national polling on the whole underestimated support for Trump by a percentage point or two, but that’s a far cry from implying polls are useless; it just means they may benefit from some tweaking.)

But what about predictions from state polls that were supposed to tell us about the electoral college? Didn’t they get it wrong?

在这种情况下，答案是:“有点，但不是真的。”Through the election season, the well-known polling and statistical modeling website538posted a continuously updated probabilistic prediction of the 2016 election outcome that integrated all state-level polls. 538 was and is considered a gold standard in the use of statistical modeling to make predictions about everything from politics to sports. And what were the odds they assigned Clinton and Trump on the eve of the election? They had a71.4% chance of Clinton winning and a 28.6% chance of Trump winning.

The first thing to note is that this indicates a high level of uncertainty. They gave Trump close to a one in three chance. So given their model based on state polls, Trump’s winning was regarded as about as likely as rolling a 2 or 4 on a single six-sided dice. Otherwise put, Trump’s win might have been surprising to most, but it actually wasn’t surprising to anyone who had a clear view of the polls: the outcome was uncertain, and Trump had a non-trivial chance of winning. (By way of contrast, similar modeling gave Obama over a 90% chance of winning on the eve of the election in 2012.)

Furthermore, shortly before the election, 538 was extremely clear that Trump had better chances in the electoral college than he did in the general. And that judgment was based on state-level polling data. Just consider a couple quotes fromthis prescient articlefrom November 1, 2016: “In fact, Clinton would probably lose the electoral college in the event of a very close national popular vote.” “If the results are tight next Tuesday…Michigan and Wisconsin are much more likely to swing the election.” Sound familiar?

Given all that, it’s clear that the polls in 2016 were still useful, as long as you used the right ones for the right questions and grant that there was a high level of uncertainty. One way polls can get things right is by telling you to be uncertain when things really are unpredictable.

So if you like using polls to keep your finger on the pulse of the electorate, you should go right ahead, as long as you use them in a balanced way. If you do this, you will be far better off than most pundits (public or private) who ignore the polls and instead have “theories” or “intuitions” about what’s going to happen. And you will also be far better off than you would be if you just relied on yourown“theories” or “intuition.”

The importance of this point, as I suggest above, is that a healthy awareness of polls can help combat propaganda and misinformation. That’s true in part because awareness ofanypolitically relevant objective information can combat those things.

But there’s also a specific narrative that’s worth combatting at this time, and polls in particular can help do it. Manyhave said—andcontinue to say—that Trump will win again, and there is often a tone of certainty to such predictions. So it’s easy to fall into doom and gloom thinking. And if you believe those who dismiss polls, then the polls won’t be an antidote to the doom and gloom. But we just saw that dismissing polls is based on sloppy thinking.

So what do the polls currently say?

Right now, thelatest polls拜登、伯尼和沃伦都以9-11%的支持率领先特朗普。此外，约52%的受访者表示，他们将“绝对反对特朗普”。当然，现在还为时过早，所以得出特朗普不会连任的结论是愚蠢的，而且总有另一种令人沮丧的前景，即普选和选举人团的分裂。与此同时，一种健康的观点告诉我们，他充其量是极其脆弱的，这与自信地预测他会获胜的错误叙述相矛盾。

Furthermore, for anyone voting in the democratic primaries, we needn’t be anxious about compromising quality for “electability”—all领先者很有可能击败特朗普。

因此，总而言之，民意调查比许多公共权威或社交媒体喷子所宣称的更值得信任，这是一件好事。And the fact that they’re trustworthy is good, because lately they’ve beenbringing good news.