Chris Hanretty Profile picture
Dec 9, 2019 16 tweets 3 min read Read on X
A number of people (n > 2) have now asked me about the effect of rain on turnout, given that it is forecast to be wet on Thursday (1/n).
This is not a stupid question. There is academic research on the precipitation/turnout link, either for its own sake or as an instrumental variable (2/n).
The most cited paper on this topic finds that *an inch* of rain over the course of the day reduces turnout by almost one percent: myweb.fsu.edu/bgomez/GomezHa… (3/n)
But an inch of rain is an awful lot. At the time of #EURef , a day which featured some localised storms, the *wettest* local authority received less than an inch of rain (23mm) (4/n)
The *average* local authority that day received around 3 mm of rain. So if we make the "average local authority" bone-dry, then turnout in that area might have increased by (3mm/1 inch) * 1 = 0.12% (5/n)
When I investigated the link between rainfall and turnout in the referendum, I found no statistically significant link: medium.com/@chrishanretty… (6/n)
Pat Leslie and Baris Ari disagree, and (after including a lot more covariates) find that an extra inch of rain would have decreased turnout by 2.45 percentage points doi.org/10.1016/j.polg… (7/n)
(This would mean that our average-to-bone-dry local authority would have seen turnout fall by 0.3 percentage points). (8/n)
Turnout effects of less than a percentage point are also unlikely to lead to very different vote shares. (9/n)
Suppose 66% of the population always votes, 33% never votes, and 1% votes only if it's clear. (10/n)
Suppose the always votes population votes

42 Con/33 Lab/25 Other

and the sometimes-votes population votes
33 Con/42 Lab/25 Other

which a big difference (11/n)
If it rains, the vote is

Con 42/Lab 33/Oth 25.

If it's dry, the vote is
Con 41.86 [(66*42 + 1*33)/67]
Lab 33.13 [(66*33 + 1/42)/67]

12/n)
So: the effects of weather on turnout are small, if they exist, and the effects on vote share are tiny (less than one fifth of one percent in an extreme case). (13/n)
If you want to fuss about *something*, fuss about whether Wednesday's news coverage will portray the result as a foregone conclusion. Expected closeness is well known to promote turnout (14/14)
p.s. If anyone can hit me up w/ a detailed raster map of election day rainfall, that would be great...
You just *knew* it was going to happen: I wrote on the link between constituency level rainfall and turnout in this election medium.com/@chrishanretty…

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More from @chrishanretty

Jun 1, 2023
In response to UCU's Marking and Assessment Boycott (MAB), my employer @RoyalHolloway has decided to implement emergency regulations which in my view seriously call into question the rigour of degrees awarded (1/7)
The regulations include allowing marks for a module to be scaled proportionately (you did 50% of the coursework; that counts for 100%) (2/7)
(cont.) to permit an unlimited number of "allow" outcomes for modules (previously used where sickness or other extenuating circumstances affected students' performance) (3/7)
Read 7 tweets
Nov 20, 2022
Everyone knows the most fun way to watch the World Cup is to support the more democratic nation in each game. So here, thanks to @vdeminstitute data, is your group-by-group rundown! (1/n)
We start in Group A, where the Netherlands is clearly in pole position, and Qatar clearly in last place (2/n) Image
In Group B, England and Wales are in a dead heat (until and unless V-Dem produces estimates of sub-state democracy), with Iran placing last. (3/n) Image
Read 11 tweets
Jul 16, 2022
This use of MRP makes me incredibly anxious. There are considerable technical difficulties here. Begin nerdgasm... (1/15)
MRP works by modelling responses as a function of different demographic and political characteristics, and then making predictions for different voter types (2/15)
It works well when responses can be accurately predicted by these characteristics, or when you have a stupidly large sample size (3/15)
Read 15 tweets
Sep 24, 2020
Towns are sexy in UK polisci, aren't they? Let's talk a little bit about the super-sexy Towns Fund gov.uk/government/pub… (1/n)
As @estwebber and @georgegrylls reported this morning, the Perm. Sec at MHCLG gave evidence to the Public Accounts Committee this week thetimes.co.uk/article/robert… (2/n)
Jeremy Pocklington said that ministers had ignored civil service advice concerning the £3.9bn Towns Fund, and had instead applied [ahem!] "their own qualitative assessment" (3/n)
Read 20 tweets
Sep 12, 2020
Strong, strong political reasons to support Osaka in this match #USOpen
Azarenka and Lukashenko have a "friendly" relationship nytimes.com/2020/09/09/spo…
But god-damn, she's started well 😖
Read 5 tweets
Sep 11, 2020
I have some reservations about the claim that Covid-19 divisions now run deeper than Brexit (1/n)
The basis for the claim is that the proportion of mask-wearers who hate, resent or think badly of non-mask wearers (58%) is greater than the proportion of Remainers who think badly of Leavers (33%) (p. 11 of report) (2/n)
First problem with this: in order for something to be divisive, it's got to divide society, and the more evenly it divides society, the more divisive it is. But the (short) report doesn't show what % of the population wear a mask. (3/n)
Read 6 tweets

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