Gur Huberman writes that he’s been wondering for many years about this question:
One function of protests is to vent out the protesters’ emotions. When do protests affect policy? In dictatorships there are clear examples of protests affecting reality, e.g., in Eastern Europe in 1989. It’s harder to find such clear examples in democracies.
And he sent along a link to this paper from 2013, Do Political Protests Matter? Evidence from the Tea Party Movement, by Andreas Madestam, Daniel Shoag, Stan Veuger, and David Yanagizawa-Drott, who write:
Can protests cause political change, or are they merely symptoms of underlying shifts in policy preferences? We address this question by studying the Tea Party movement in the United States, which rose to prominence through coordinated rallies across the country on Tax Day, April 15, 2009. We exploit variation in rainfall on the day of these rallies as an exogenous source of variation in attendance. We show that good weather at this initial, coordinating event had significant consequences for the subsequent local strength of the movement, increased public support for Tea Party positions, and led to more Republican votes in the 2010 midterm elections. Policy making was also affected, as incumbents responded to large protests in their district by voting more conservatively in Congress. Our estimates suggest significant multiplier effects: an additional protester increased the number of Republican votes by a factor well above 1. Together our results show that protests can build political movements that ultimately affect policy making and that they do so by influencing political views rather than solely through the revelation of existing political preferences.
My reaction: I’m suspicious of any analysis involving rainfall in that way. Ultimately it’s observational data and I think these sorts of tricks are hocus-pocus. That said, I do think protests can make a difference (I’d say this whether or not I’d seen this particular paper you sent me).
The usual story I’ve heard, and which makes sense to me, is that protests energize the base, motivating people to write their congressmember, run for office, harangue their friends and relatives about politics, etc. It’s not about the direct effect of intimidating politicians (although maybe that’s part of it) or even about the effect of swaying public opinion to your side—as many people have noted, protests can often antagonize the average voter. Rather, it’s about getting potential core supporters more involved in politics.
After I sent that response to Gur, he sent me his take on the Madestam et al. paper:
The point of the very clever paper: Just correlating protest size & voter sentiment doesn’t prove that protest size affects voting outcome; possibly (likely) both are affected by voter sentiment. Now, think about two otherwise identical places, A & B running parallel protests. Suppose it rains on A and not on B, and therefore the protest size in A is smaller than that in B. A difference in voting outcome (more protest-sympathetic vote in B) is reasonably attributable to the lower protest turnout in A which in turn is attributable to rain, not to sentiment.
OK, I should elaborate: Sure, I realized from the abstract that this is what was being done in this paper, and I agree that the rainfall-instrument is clever and worth trying out. But I don’t think the result is necessarily as clean as it might appear. The difficulty is the “otherwise identical places” thing. Places aren’t really otherwise identical. Or, to put it another way, the rain in different places on that day was not random; the data are correlated. And various other issues too. Looking through the paper, I see that the authors do seem aware of many of these issues, and on first glance it looks much better than, say, the air-pollution-in-China paper. Still, I don’t know that I’d trust the result of this sort of instrumental analysis as much as I’d trust a more conventional analysis, where cities are matched on a bunch of pre-treatment variables and then regression models are constructed to predict the outcomes of interest.
I do find the idea of instrumental variables appealing in this context: after all, the “treatment” (in the sense of a potentially manipulable intervention) has something to do with various key actors in politics and the news media. Or, to put it another way, there are two sorts of decision makers here. There are the political leaders or political entrepreneurs who make the decisions of whether and how to organize rallies, and there are all the individual people and groups that decide whether to participate in a rally. And it makes sense to me to think of the size of a rally as an intermediate outcome, as the result of all those decisions. So in that sense I’m thinking in terms of instruments.
But I don’t really buy the rainfall thing; it strikes me as an attempt to get something for nothing. Remember my trick for thinking through instrumental variables? The usual approach would be to say that the instrument gives us an effect of the effects of crowd size. Instead I’d say that excess rainfall on that day is correlated with crowd size and with some other political outcomes. That’s about it. And given the spatial correlations of weather patterns, it’s more of an N=5 or N=10 thing than N=2758. Again, it’s a serious analysis, and there’s no reason not to look at it. I’m not trying to shoot it down so much as to clarify its interpretation.
The big picture is that the causal mechanisms suggested by Madestam et al. are similar to what I’ve heard people say over the years, based on qualitative evidence. So maybe it’s not so important how seriously we take their particular quantitative claims. Setting research methods aside, our best answer to the question of how protests affect policy is that they do so by mobilizing activists and potential activists who can then go out and do political activity and persuasion.