Waiting for a Priest

This is part one of a two-part article I wrote for the always excellent Perspective Magazine. I've posted a few snippets on my profile, but here's part one (which was published under the title Data isn't Evidence) in its entirety.

In case there's anyone who wants to pick up where the extracts left off, I've written 'FROM HERE' at the appropriate point in the text.

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There’s a sort of ‘received view’ of science according to which theories simply emerge from an unprejudiced engagement with the data. Hence the common refrain: “Just follow the data!” or the claim that this or that idea is ‘evidence based’.

This picture of science carries the dangerous implication that any two honest and competent people who survey ‘the data’ must, necessarily, agree with one another.?

Which means, of course, that anyone who doesn’t agree with a competent analysis of data must be ignorant; or deliberately ignoring the data; or incompetent; or stupid; blinded by some malevolent ideology; or, in that insult so beloved by the intellectually bankrupt, ‘lying’.?

How many times have you seen those sorts of allegations flying around on social media, or in the opinion pieces of certain journalists, and in the mouths of certain phone-in show hosts?

As we shall see, this view of science is absolutely wrong.?

Let’s begin by going back to mid-19th century Vienna. At that time, there were two maternity wards in the city’s General Hospital, Ward 1, and Ward 2.?

Life in Ward 2 was normal enough, but Ward 1 was notorious. So notorious that pregnant women would often beg not to be taken there. Indeed it became common for women to refuse to enter the hospital at all; preferring to give birth in the street rather than be admitted to the dreaded “ward of death”.?

What was the problem??

Well, in Ward 2 the maternal mortality rate was around four per cent – about average for the time – but in Ward 1 it was a very different story. There, for every ten women who were admitted, only nine came out alive. The rest succumbed to the mysterious “childbed fever”.?

In July 1846, the hospital appointed a young doctor named Ignaz Semmelweis. Semmelweis was determined to get to the bottom of the deadly mystery.?

He was immediately able to reject most of the theories floating around.?

Perhaps the poor diet in Ward 1 was the problem??

No, the food was the same in both wards.?

Perhaps Ward 1 was overcrowded??

No, the wards have the same number of beds and there were fewer patients in Ward 1.

However, there was a more promising explanation that relied on psychological trauma.?You see, whenever anyone was close to death, the hospital sent for a priest to administer the last rites. One of the doctors pointed out that because of the building’s layout, the priest would have to pass through Ward 1 regardless of his ultimate destination.?Perhaps the sight of the sombre priest and his assistants in their last rites garbs filled the women with dread, and in some cases, scared them to death?

An interesting theory.?

Naturally, Semmelweis had to consider the data.?But what data should he consider? Well, he could have taken note of the colour of the priest’s shoes; or the name of the horse that pulled his carriage; what about the prior activities of the doctors working on the ward? Or the type of soap each person had used that morning? How about the number of leaves in Vienna Woods??

Quite absurd of course.?None of these is relevant and Semmelweis quite rightly ignored them all.?

Ok, but why mention them?

Well, the absurdity throws a crucial distinction into sharp relief: not all data count as evidence; only relevant data does.?This may strike you as trivially obvious. If so, let me ask you what determines which data count as relevant and which do not? It’s really worth pausing for a moment to consider this.?Why, for example, was the presence of a priest on the ward relevant, but the number of leaves in Vienna Woods not? It can be tempting to pull yourself up by your own bootstraps and say something like:?

“Well, one is relevant and the other just isn’t.” In fact, the thing that determines which data are relevant is … the theory through which you view the issue.?Theories do not simply emerge from raw data. On the contrary, the theory we use determines the tiny fraction of data that we count as evidence.?

FROM HERE

By the way, just to be clear, I’m not suggesting that theories are formed in complete independence of data.

Anyway, to illustrate the relationship between theories and relevance a little further, let’s go back to Vienna. Semmelweis made sure that priests took a different route through the hospital; avoiding Ward 1. Now all he had to do was to wait for the new maternal mortality data.?Sadly, it had made no difference. The dreadful mortality rate remained, and the psychological theory was itself dead. Semmelweis described himself at this time as being “like a drowning man searching for a straw.”

Then tragedy struck. A close friend of Semmelweis; a fellow doctor in the hospital, became very ill. On visiting his friend, Semmelweis noticed he had the symptoms of childbed fever. He also noticed an infected wound on the man’s finger. In a lucid moment, the doctor was able to tell Semmelweis he’d cut himself on a student’s scalpel. The student, it transpired, had just been using the scalpel to perform an autopsy.

Could there be a connection??

It’s essential to remember that there was no concept of microbes or bacteria, let alone the germ theory of disease. Indeed, the hospital authorities thought Semmelweis’ latest conjecture was outlandish. ‘Some kind of dangerous invisible force? What nonsense, next you’ll be telling us it was evil spirits!’

Nevertheless, he carried on. Once again, the building’s layout seemed important. Ward 1 was close to the morgue, and so students often went there immediately after performing an autopsy. Ward 2, on the other hand, was in a distant wing and students rarely went there straight from the morgue.

Could “cadaveric matter” somehow be the culprit? Semmelweis insisted that, from now on, everyone entering the maternity wards must thoroughly wash their hands in a chemical solution to rid themselves of cadaveric matter.

It worked! In 1848, the death rate in Ward 1 fell from 10% to 1.27%; in Ward 2, it fell to 1.33%.?

Of course, Semmelweis ‘cadaveric matter’ theory separated relevant from irrelevant data in its own way. Now the prior activity of the people working on the ward was relevant, but the presence of a priest on the ward wasn’t.

Alright, how does all this relate to economic policy?

As we’ve seen, the theory through which you view the world determines the data you pay attention to, and the data you ignore.? According to the psychological theory, a priest passing through the ward on his way to deliver last rites was important data that could be used to predict excess deaths.?In answer to the question: Are excess deaths coming?? the adherent of the psychological theory would answer “Let’s wait and see if a priest walks through the ward. If no priest comes, we will be safe.” This, in my view, is the kind of thing that happened in the Bank of England. You may recall, in early 2021, the Bank’s pronouncement that inflation wasn’t about to hit. They were sure because in their words: “Inflationary expectations are well anchored.”??

According to their models, if there was inflation on the horizon, it would show up in the data on inflationary expectations.?

That is wrong.?

It is in the nature of a new inflationary episode to take everyone by surprise. This is its power, and why it does so much damage. The Bank’s pronouncement was based upon an incorrect theory of the economy according to which the private sector immediately adapts its behaviour to any change in government policy. If that were true, inflation would have hit (in a relatively harmless way) as soon as the massive increases in the money supply took place during the pandemic.?

Why did the Bank miss the coming inflation? Because their theory of the economy drew their attention to the wrong data; they were waiting for a priest to walk through the room. And because no priest came, they thought they were safe.?

#inflation #perspectivemagazine