When did we become gluten intolerant?

I don't know about you all, but I've been doing this since the early 2000s.

The dynamic information equilibrium approach I talk about in my recent paper doesn't just apply to economic data. The idea that the information content of observing one event relative to observing another event has rather general application. As an example, I will look at search term frequency. Now if the English language was unchanging, given that there are a huge number of speakers, we'd expect relative word frequencies to remain constant and the distributions to be relatively stable. Changes to the language would show up as "non-equilibrium shocks" — a change in the relative frequency of use that may or may not reach a new equilibrium. A given word becomes more or less common and therefore has a different information content when a that word is observed (a "word event").

We might be able to see some of these shocks in Google trends data — a collection of "word events" entered as search terms. It's is only available since 2004, so we really can only look at language changes that happen within a few years. Longer changes (e.g. words falling into disuse) won't show up clearly, but this time series is well-suited for looking at fads.

I wanted to try this because I read an offhand comment somewhere (probably on Twitter) that said something like "everyone suddenly became gluten intolerant in 2015" [1]. What does the search data say?

The gluten transition in the US is centered near January 2009, but takes place over about 6 years (using the full width at half maximum for the shock). It "begins" in the mid-2000s and we seem to have achieved a new equilibrium over the past couple years.

How about avocado toast? That happened around 2015 in the US:

However, I did notice on Twitter there were a lot more and earlier references to avocado toast from Australians (in fact I think it was a mention in Australian media that it wasn't just the breakfast I made myself for years after having been given it by a Chilean friend where it's been a common dish for a long time ("palta")). Was this hunch visible in the data? Yes — almost a full year earlier:

So anyway, I just wanted to show a fun application of the information equilibrium framework. It applies to a lot of situations where there is some concept of balance between different things: supply and demand, words and their language, cars and the flow of traffic, neurons and the cognitive state, or electrons and information.

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Update 2 February 2018

The "macro wars" (Nov 2007–Mar 2011):

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Footnotes:

[1] Update: found it.

As a casual student of American food faddism, something that is still more than alive and well today (Yes, it’s an amazing coincidence that a sizable percentage of the educated liberal upper middle class all became gluten intolerant over a 3 year period. Must be pollution or something), I always love stories about our ridiculous food history.

It's a 6-year period above, but the definition of the "width" of a transition is somewhat arbitrary (I used the full width at half maximum above).