Outta Nowhere! 430 Projections for Clinton-Trump

08 November 2016

Back in January, I introduced the 430 Model for using polls to forecast elections. The name comes from the idea that you get 20 percent of your results from 80 percent of your work, and I only wanted to do about 20 percent of what Nate Silver does with FiveThirtyEight.

Since then I’ve wanted to do a bigger and better version for the general election. But since I’m the kind of guy who only wants to do 20 percent of the work, most of that didn’t happen. But I do have a slightly bigger and better version! So that’s something.

As before, I’m using the poll data from the Pollster API, combining the results and weighting by age to create a super-poll. Then I’m running 10,000 simulations using the results of the super-poll to figure out how likely each candidate is to win.

The code for this version is in a Jupyter notebook on GitHub, so you can play with it if you want to pretend Jill Stein matters or something.

Now to the results! Using the super-poll results since July, the race has looked like this:

Clinton is winning by a lot in the super-poll

Those lines are the 95% confidence bands. The story here is that, while things were pretty uncertain early in the race, Clinton began to separate after the first debate in September, and Trump has never been able to catch up. The recent revelations about the emails, for all the sturm und drang they caused, don’t really show up here. She’s just ahead. How ahead? This ahead:

CandidateMeanStandard Deviation
Hillary Clinton48.4%(0.2)
Donald Trump42.7%(0.2)

Well, she’s not over fifty. But five and a half points is a pretty solid lead with as many polls as we’ve had. In 10,000 trial simulations, she won every single one. That’s as comfortable as you get.

So, any caution? If, as many suspect, there’s a weird Trumpian version of the Bradley Effect, then he has a better chance than the model projects, which is none. But with 0.2 percentage points standard error, he needs to get to swing better than two and a half points if he’s drawing them all from Clinton, and More if he’s getting them from the Other category. In the best case, that’s one secret supporter to every public one. That’s a tough road to hoe.

Still, this is a strictly poll-based model. If the polls are systematically wrong, then so is the model. We didn’t really see systematically wrong polling in the primaries, though we have seen it in votes abroad, such as Brexit. But that has to be the hope, if you’re a Trump supporter: that the polls are almost all wrong and in the same way.

My gut says no. Clinton’s got this one.

Why aren't you using make for your data projects?

07 April 2016

Data work can take a long, long time. Once you’ve moved beyond small scale projects, you just have to get used to doing something else while your machine chugs away at cleaning, preparing, or analyzing your data. And since most of the time you have to try a few things to see what comes out, you’ll have to do sit and wait through multiple rounds of each step.

But a lot of people make it worse by doing one of two things: either they have one big script which they re-run from start to finish every time they make a change, or they run each step on-demand (say, in an Jupyter notebook), and mentally keep track of what they need to do in what order.

The first is bad because every single run will take the whole run time, and your life will be swallowed up in waiting. The second is bad because you have to depend on yourself to keep what can be a pretty intricate map of your analysis flow in your head.

The Unix utility Make provides a better solution. Make is the old standard build system, designed to help with the compilation of large programs. Just like with data projects, compiling large programs takes forever, has a variety of smaller steps where you might need to go back and edit something, and has a web of dependent steps you might need to re-run depending on what you’ve changed. In other words: it’s a perfect fit.

What’s more, Make helps you keep your steps separate computationally, which helps you keep them clear conceptually. You don’t even have to use the same language with each step: I’ve had occasion to mix Python, Scala, and Stata in the same project,1 and make made that much less painful.

And here’s the good news: if you’re on a Mac or Linux, it’s probably already installed. On windows, just install Gow.

So how does it work? The basic idea is, you write a makefile filled with recipes that tell you how to make a target. Each target can have dependencies, and if a dependency has been modified more recently than the target, the recipe for the target gets re-run.

So let’s say I want to classify some text in a folder, using some trainers in another folder. Both have to be prepped for analysis, using a script in my scripts subdirectory. I might put the following recipe in my makefile:

data/clean/trainers.csv: scripts/clean_text.py data/raw/trainers
    python -o data/clean/trainers.csv scripts/clean_text.py data/raw/trainers

What’s going on here? The file before the colon is the target, the thing we’re trying to make. The files after are dependencies, things that need to be made before the target. The line beneath, which is indented by a tab—yes, a tab—is the command that makes the file. Now, if we were to run make data/clean/trainers, make would check to see if either the clean_text.py script or the trainers directory2 had been modified more recently than the output file, and if so, it would run the script to create the file.

We can write this recipe a simpler way:

data/clean/trainers.csv: scripts/clean_text.py data/raw/trainers
    python -o $@ $^

In a makefile, $@ stands for the target, and $^ stands for the list of dependencies in order. This means if our dependencies are a script and a list of arguments to that script, we can use them as a stand-in for the recipe.

Now let’s say we use the same script to clean the unlabeled input. We just need to add it as a new target:

data/clean/trainers.csv: scripts/clean_text.py data/raw/trainers
    python -o $@ $^

data/clean/unlabeled.csv: scripts/clean_text.py data/raw/unlabeled
    python -o $@ $^

Easy! Now if we update clean_text.py, Make knows we need to remake both those targets. But I hate repeating myself. Luckily, Make gives us canned recipes:

define pyscript
python -o $@ $^

data/clean/trainers.csv: scripts/clean_text.py data/raw/trainers

data/clean/unlabeled.csv: scripts/clean_text.py data/raw/unlabeled

In fact, since I write all my scripts based off of the same boilerplate, let’s fill out what the whole project might look like:

define pyscript
python -o $@ $^

data/results/output.csv: scripts/classify.py data/classifier.pickle data/clean/unlabeled.csv

data/classifier.pickle: scripts/train_classifier.py data/clean/trainers.csv data/trainer_labels.csv

data/results/analysis.csv: scripts/tune_classifier.py data/clean/trainers.csv data/clean/unlabeled.csv

data/clean/trainers.csv: scripts/clean_text.py data/raw/trainers

data/clean/unlabeled.csv: scripts/clean_text.py data/raw/unlabeled

So that’s five scripts total: each reasonably separated and able to be dropped into other projects with minimal modification. If we change any of them, either because of a bug, or because we wanted to try something different, we can use make to update only those parts that are dependent on the chain. And if we just type the command make, it automatically makes the first recipe, so we can be sure that our output.csv is using all the latest and greatest work we’ve put in.

There’s a lot more to Make, and I’ll focus in on a few features, tips, and tricks in an occasional series here. It’s been a big help to me, and if you find it helpful too, I’d love to hear from you!

  1. I said I did it, not that I’m proud of it.↩︎

  2. The directory itself, mind you, not the files inside it!↩︎

You Asked For It: 430 Model Projections for Iowa

09 February 2016

Just before the Iowa Caucuses, I showed how you can make a 80-percent-of-the-way there poll-based election forecasting system with surprisingly little work. I called it the 430 Model, because 430 is about 80 percent of 538, and I was ripping off Nate Silver. My model did OK on the Democratic side, though (like the polls) it was off on the Republican side; Trump’s support was overstated, or rather the opposition to Trump was understated.

But, since people have been interested, I’ve updated the model a bit and made forecasts for New Hampshire! I’ve simplified the weighting decay function to halve the weighted sample size for a poll each day1. I’ve also added limited my results to polls with likely voter screens, and set the window of polls included in the super-poll by number instead of by date. You can download and play around with the new model as a Jupyter notebook here.

So, let’s get to the fun!

This is what the New Hampshire race has looked like over the last three weeks on the GOP side, when polling has happened pretty steadily:

New Hampshire GOP Chart

The picture’s been pretty stable the whole time. There’s three tiers: the down-and-outs (Christie, Fiorina, Carson), the hope-for-seconds (Rubio, Kasich, Cruz, Bush), and Trump. The superpoll results bear that out:

CandidateEstimateStandard Error
Donald Trump31.2%1.7%
Marco Rubio14.5%1.3%
John Kasich13.8%1.2%
Ted Cruz11.7%1.2%
Jeb Bush11.0%1.1%
Chris Christie5.8%0.8%
Carly Fiorina4.6%0.7%
Ben Carson2.6%0.6%

Rubio’s bump has gotten him to the top of the second tier, but realistically those guys are all tied, and each of them (except Cruz) really, really wants a second place finish. First place seems utterly out of reach for all of them; in my 10,000-trial simulation, Trump won every single time.

On the Democratic side, things seem equally fatalistic:

New Hampshire Dem Chart

Not even a story there. Bernie Sanders is winning. So also says the superpoll:

CandidateEstimateStandard Error
Bernie Sanders55.1%1.9%
Hillary Clinton40.9%1.9%

As Trump did on the GOP side, Sanders wins every time in a 10,000-trial simulation.


Polls have historically been bad in New Hampshire. These projections are a great summary of what the polls are telling us, but if the polls are consistently off by a significant amount, we could still get some real surprises. If I were Sanders or (especially) Trump, I would actually wish my numbers were a little worse; in both cases, not dominating is going to look like a loss. It’s entirely possible that one of those second-tier GOP candidates is really going to break out, though I have no idea who it would be or why.

Or maybe they’ve finally learned how to poll New Hampshire and this is all effectively a done deal. We’ll find out tonight!

  1. This sounds more extreme than it is. A poll with 300 respondents has a margin of error of about 2.9 percent, one with 150 respondents about 4.1 percent, and one with 75 respondents about 5.8 percent. When you think about how many people can change their minds every day during an election, that looks reasonable to me.↩︎