Many years ago in Paris, Arkansas, there was a small shop owned by a local family named Kafka. I never met them and have no idea what relation they had to the writer.
The shop was of a very common type in the Ozarks, folksy with more often than not a made-in-Taiwan hillbilly décor. I don’t recall ever going inside but I do remember the sign which read something like this:
Krafts
Antiques
Fun Stuff
Kwilts
Art Supplies
This memory is not all that relevant but then neither is this post. It would have been had I written it when I first intended to a month or two ago. Back then, economic indicators and forecasts probably probably had a bigger roles in the models of 538 and the Economist. I’d imagine now it’s all about weighing polls and estimating turnout. But even if I missed the timeliness window for this post, there are some less ephemeral issues I still want to hit.
On some level, all predictive modeling relies on the assumption that the important relationships and trends we’ve observed in data in the past will continue to hold in the future. We don’t talk about it all that much but this is one of those things that makes all competent statisticians at least a little worried. This is especially true when we go out of the range of our data, when the variables we put into our model start having values we’ve never seen before.
Pretty much serious election models factor in the economy and where it’s going. The actual relationship may be complicated but, at the risk of oversimplifying, an economy that’s good or trending up favors the party in power and vice versa.
But what happens when the economy is good for half the people and terrible for the rest? Many economists have described our current situation as a K-shaped recovery with white-collar knowledge workers doing fairly well while those in other sectors such as the service industry suffering horribly.
As far as I know, we haven’t had a presidential election during a K-shaped recovery, at least not since we starting scientific polling. This is outside the range of data (as is the pandemic, as is having a president openly undermining the election, as is…). This is where the art of modeling kicks in. The statisticians at 538 are smart and experienced and I have faith in their judgement.
But when you read credulous story about model confidently predicting some wildly counter-intuitive development, it is also good to remember that modeling is a mixture of science and art and some people aren’t very good at the latter.