17th Century London: How Plague Deaths Shaped Behavior & Survival

In the face of a deadly epidemic, residents of 17th-century London didn’t simply succumb to fate. New research reveals they actively used available data – in the form of weekly mortality reports known as ‘Bills of Mortality’ – to make critical decisions about their daily lives, demonstrating a surprisingly sophisticated understanding of public health risk centuries before the advent of modern epidemiology.

The study, published in Accounting History, centers on the Great Plague of 1665, which ravaged London, claiming an estimated 68,596 lives according to official records, though historians believe the actual death toll may have been closer to 100,000. Researchers at the University of Portsmouth examined the diary of Samuel Pepys, a prominent figure of the time, to understand how he and others interpreted and responded to the weekly reports detailing the number of plague deaths.

These ‘Bills of Mortality’ weren’t simply dry statistics. They listed deaths parish by parish, specifying the cause, including plague. Sold by subscription and posted publicly, they became essential reading for Londoners seeking to understand the spread of the disease. The research highlights how this data shaped behavior, influencing where people traveled, who they met, and whether they chose to remain in the city or flee.

“Pepys wasn’t just recording history, he was using death figures to decide how to live,” explains Professor Karen McBride, School of Accounting, Economics and Finance at the University of Portsmouth. “His diary shows us, week by week, how published death numbers shaped fear, behaviour and trust in government.”

The findings challenge the notion that people in the 17th century passively accepted their fate during outbreaks. Instead, they actively sought information and used it to mitigate their risk. Wealthier families, for example, often chose to temporarily leave the city when death tolls rose in specific areas, as documented in Pepys’s diary. Merchants adjusted their routes, avoiding neighborhoods with increasing case numbers.

The Bills of Mortality functioned as an early form of public health data, a way to measure the intensity of infection long before the concept of epidemiology existed. In a city rife with rumors and anxiety, the printed death totals provided a crucial point of reference. This moment represents a turning point in the development of modern public health governance, centuries before the development of contemporary epidemiological tools or digital dashboards.

The study also sheds light on how authorities utilized the weekly data. As deaths increased, officials implemented increasingly stringent measures, including quarantines, the closure of theaters, restrictions on gatherings, and the isolation of infected households. The data, not only informed individual decisions but also justified unprecedented government interventions, including the suspension of everyday liberties.

Interestingly, Pepys didn’t blindly accept the figures presented in the Bills. He acknowledged potential undercounting and flaws in reporting, yet still treated the data as serious evidence of risk. His engagement with the data was also informed by earlier work, such as John Graunt’s analysis of the Bills, which produced some of the first mortality tables and laid the groundwork for actuarial science and life insurance. During the plague year, this type of numerical reasoning permeated daily life.

The research underscores striking parallels with how data is used today during health outbreaks. Modern public health officials rely on real-time data to track the spread of disease, implement interventions, and communicate risk to the public. The study suggests that the fundamental human response to a public health crisis – seeking information and using it to make informed decisions – has remained remarkably consistent over the centuries.

The Great Plague of 1665 serves as a historical reminder of the power of data in navigating public health emergencies. It demonstrates that even in the absence of advanced medical technology, informed citizens and responsive governance can make a difference in mitigating the impact of a deadly disease. The lessons learned from this period continue to resonate today, as we grapple with new and emerging health threats.