Tag Archives: prediction

Prediction or Explanation?

A couple weeks ago political scientist Jacqueline Stevens attacked her own discipline on the opinion pages of the New York Times. Her critique, as portrayed in the piece’s title, was that political scientists are “lousy forecasters.”

Many political scientists have responded to Stevens’ piece, from different angles and levels of rage, but one theme I’ve noticed is people disputing the assumption that political science’s goal is to make forecasts. For example, this recent letter to the editor of the Times by a professor emeritus of political science at the University of Iowa:

Forecasting is a very specialized field in political science, limited to predicting election outcomes, and the record in that field is impressive. But that is not what most political scientists do.

Political science, like most social sciences, seeks explanation rather than prediction. Its aim is to explain puzzling phenomena by relating them to phenomena that are well understood. Much of science consists of trying to resolve puzzles in that way.

I actually think prediction is what the majority of political scientists do. The distinction is that Stevens focuses on a couple of extraordinary historical cases, whereas most political science predictions involve more specific data sets. For example, theory might say that when we apply experimental treatment X, Y will increase or decrease. Or, someone might claim that Republicans give more to charity than Democrats, which is a prediction about what a data set of party identification and giving behavior would reveal.

It’s hard for me, in contrast, to think of a political science example of explanation that is divorced from prediction. I suppose the idea is to find a historical case–let’s take Stevens’ case of the end of the Cold War–and try to predict it retrospectively. But then why wouldn’t the prediction there apply to any future situations–why wouldn’t it also be a forecast? If the idea is that every historical case has to be considered on its own and that as a result their explanations tells us nothing about the future, I don’t know if that is science at all.

‘Science isn’t stagnant’

“The attitude was Apollo solved most of these questions and now it’s time to invest in other planetary bodies,” said Chip Shearer, a senior research scientist at the University of New Mexico. “But in science, things aren’t stagnant, and we’re always looking for how to improve a model based on new observations and when to throw one model out because it doesn’t explain enough.”

From an article in today’s Boston Globe.

I’m waiting for the op-eds slamming government funding of the space program (what’s left of it anyway) for supporting “research that is amenable to statistical analyses and models even though everyone knows the clean equations mask messy realities that contrived data sets and assumptions don’t, and can’t, capture.”

How predictable are American elections?

Nate Silver had a thorough post the other day (June 6) about how well economic models predict the results of US elections. Silver goes through several economic indicators and how well they predict election outcomes, and also tries to deconstruct Douglas Hibbs “bread and peace” model, which predicts election outcomes remarkably well using only two variables, change in real disposable income and whether there is a war. Here I think is the main point of the piece:

This seems like a healthy state of affairs. Simple economic variables can account for a little less than half of the variability in election results. The other half falls into the “everything else” category, including factors such as foreign policy successes and failures, major scandals, incumbency, candidate quality, controversial social legislation and structural factors like changes in partisanship. Technically speaking, some of the variability may also be explained by economic factors that weigh upon voters’ minds, but which are not easily quantified by measures like G.D.P. and inflation.

That’s a nice story, but I’m not sure how much I believe it, even considering Silver’s critique of Hibbs.

Is politics unpredictable?

Chris Cillizza and Aaron Blake seem to think so.

The death of Osama bin Laden proves, yet again, that politics is the most unpredictable of businesses.

President Obama’s announcement late Sunday night that bin Laden had been killed in a firefight in Pakistan came as a shock to a political world in which the war on terrorism had receded as a defining issue in recent years.

While it’s too soon to draw broad conclusions about what the death of bin Laden will mean in raw political terms, it’s not too soon to conclude that his demise will re-adjust the political world — at least in the short term — in a meaningful way.

[...]

Remember that moments matter in campaigns, particularly when they are as unpredictable and unexpected as this one. The vote for president is ultimately a vote for the person best equipped to represent and lead the country.

So, um, politics is unpredictable, but moments are what systematically “matter” in campaigns? Seems contradictory. If politics is unpredictable, then nothing really matters. Also, if that last sentence of theirs that I quote were true, then it would be evident in the data. But this is not what the data show. In truth, moments don’t seem to matter much. It’s not entirely mysterious why they don’t, either.

Another person who thinks politics is random is this letter-writer in the Globe the other day, writing about a related topic:

I AM compelled to write this letter because of our government’s seemingly irrational and random reaction to genocide and tyranny around the world. We commit military power in Libya, but sit idly by while hundreds, if not thousands, are brutally attacked or killed in Syria. We have allowed millions to die in Darfur, and even greater millions to perish in Congo, and America allows women and children to be raped, mutilated, and sold into sexual slavery all around the world.

It’s not hard to think of some explanations for the patterns of US intervention. I know less about this topic, but there are many people who study interventions systematically. But it’s probably a reasonable interpretation of events for readers, if they depend on people like Cillizza and Blake to interpret the world for them.