Your Postcode Was Your Prognosis

There is a moment in Victorian public health history that should be more famous than it is. A man called William Farr was sitting in the General Register Office in the 1840s with nothing but a pile of death certificates and a register of house rents when he noticed something that stopped him cold. The streets where people were dying of cholera were not simply poor streets. They were streets where the rent was low. And the relationship was not vague or approximate – it was almost mathematical. Stack the mortality figures next to the rent book and the two columns mirror each other so precisely that you could, in principle, predict a neighbourhood's death rate without examining a single body.

When the Rent Roll Was the Medical Record

Farr was not a doctor in the field. He was a statistician, essentially, and what he had stumbled onto was this: health was not primarily a question of individual bodies but of addresses. The cholera didn't much care who you were – your constitution, your temperament, your diet. It cared enormously about where you lived. How many people shared your rooms. Whether your yard drained into a sewer or a cesspit. Whether your landlord had bothered with a water pump. All of that got compressed, neatly and ruthlessly, into your weekly rent.

Low rent meant overcrowding. Overcrowding meant one tap between forty people and a privy that backed up every summer – the kind of courtyard that never got direct sunlight, where the air was thick with what Victorians called "miasma" (they had the wrong mechanism but entirely the right instinct – the smell was the sign that something was wrong with the water). A few streets away, in the same city, a household paying twice the rent was breathing different air, drinking different water, and dying at a fraction of the rate.

For more on the curious accidental laws that shaped British public life, The Accidental Law That Made Going to the Cinema Safe Enough to Bother is worth your time.

The Germ Was Not the Whole Story

What is strange about this, looking back, is that the germ theory of disease had not yet arrived. John Snow famously mapped the Soho cholera outbreak onto a water pump in 1854, but the idea that a specific microorganism was the culprit only hardened into scientific consensus later in the century. Farr's insight came earlier. It was essentially sociological rather than medical. The unit of analysis was not the patient. It was the street.

Does the link between rent and death rates still hold?

The uncomfortable truth is that the postcode never really stopped being a prognosis. Researchers tracking health outcomes in modern Britain still find that your likely age at death is bound up with where you grew up, what kind of housing your parents could afford, how much green space you had access to, what your local air quality was like. The machinery of cause has changed – we are not frightened of cholera any more – but the basic shape of Farr's discovery has proved remarkably stubborn.

What looks like a story about infectious disease turns out to be a story about rent, landlords, and pipe-work. The body was almost the last thing it was about.