New research from the University of Portsmouth reveals that during the Great Plague of 1665, Londoners relied on published death statistics to make critical daily decisions about where to go, whom to meet, and whether to flee the city. The study demonstrates that weekly mortality reports, known as the Bills of Mortality, served as an early form of public health data that shaped both individual behavior and government policy in unprecedented ways. Drawing extensively on the famous diary of Samuel Pepys, the research shows how these numerical accounts became powerful tools for managing both populations and personal risk during one of history's deadliest epidemics.
The findings challenge the common assumption that data-driven public health is a modern invention. Instead, they reveal how the systematic counting of deaths became a political and social instrument that expanded government authority while simultaneously shifting responsibility onto individuals to manage their own safety. The research, published by Sage, offers striking parallels to how societies today use data during health crises, raising timeless questions about the balance between protection, power, and personal freedom.
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The Bills of Mortality: London's First Public Health Data System
The Bills of Mortality were weekly statistical reports that documented deaths across London's parishes, listing both the total number of deaths and their attributed causes. According to Professor Karen McBride of the University of Portsmouth, these reports represented a fundamental shift in how governments managed public health crises. During the Great Plague, which killed an estimated 100,000 people in London alone, the Bills became essential reading for anyone trying to navigate the deadly landscape of the city.
The research, published in the journal Accounting History, uses a microhistory approach to examine how Samuel Pepys, Clerk of Acts to the Navy Board and member of the Royal Society, engaged with these mortality statistics. Pepys mentioned the word "plague" 150 times in his diary during this period, demonstrating his intense focus on tracking the epidemic's progression. His diary entries reveal a man who was not merely recording history but actively using death figures to determine his daily actions and assess the level of danger in different parts of the city.
Far from being dry statistics, these weekly reports influenced fundamental decisions about movement, social interaction, and survival. The Bills helped justify unprecedented government interventions, including quarantine measures, travel restrictions, and the suspension of everyday liberties. This marked a significant transformation in the role of government, as public authorities took on responsibilities that had previously belonged to the monarchy and the church.
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Portrait of Samuel Pepys (1633-1703) (John Hayls/Public Domain)
Samuel Pepys: A Diarist Using Data to Navigate Disaster
Professor McBride's research highlights how Pepys was not simply a passive observer but an active user of accounting information for decision-making purposes. "Pepys wasn't just recording history, he was using death figures to decide how to live," McBride explained in a press release from the University of Portsmouth. "His diary shows us, week by week, how published death numbers shaped fear, behaviour and trust in government. It's one of the earliest examples of data being used to manage both populations and personal risk."
The diary provides a ground-level view of how an educated, relatively wealthy Londoner processed and responded to epidemiological data. Pepys tracked the weekly increases in plague deaths, noted which parishes were most affected, and adjusted his movements accordingly. His entries demonstrate an intuitive understanding of risk assessment based on numerical evidence, showing how individuals used rudimentary forms of accounting information to enhance their prospects of survival.
This represents what scholars call an "instinctive, rudimentary use of accounting information" to guide fundamental life-and-death decisions. The research contributes to a growing literature that examines how non-conventional forms of accounting can drive judgments and decision-making, even in the absence of formal training or sophisticated analytical tools.
A Bills of Mortality document from 1665, showing weekly death statistics by parish and cause. (Wellcome Collection/CC BY 4.0)
The Inequality of Information: Who Could Afford to Flee?
While the Bills of Mortality provided valuable information to those who could access and interpret them, the research also reveals how their impact was deeply unequal. Wealthier Londoners like Pepys possessed both the literacy to read the reports and the financial means to act on the information they contained. When the death tolls rose alarmingly, affluent residents could leave the city for safer rural locations, effectively using data to save their lives.
In contrast, poorer residents living in overcrowded conditions had less access to information and fewer options for escape. They were more likely to be exposed to the plague, more likely to be subject to restrictive quarantine measures, and more likely to be left behind as the wealthy departed. This created a situation where public health data, while ostensibly neutral, reinforced existing social inequalities and determined who lived and who died.
The Bills of Mortality thus served a dual function: they empowered those with resources while simultaneously documenting the disproportionate suffering of the poor. This pattern of unequal access to life-saving information during epidemics remains relevant today, as modern societies continue to grapple with disparities in health outcomes based on wealth, education, and social position.
Lessons for Modern Pandemics
The parallels between the Great Plague of 1665 and modern health crises are striking. Today's societies similarly rely on published statistics about disease prevalence, mortality rates, and geographic spread to guide both government policy and individual behavior. The COVID-19 pandemic demonstrated how daily case counts and death tolls shape public fear, compliance with restrictions, and trust in authorities, much as the Bills of Mortality did more than three centuries ago.
The research raises important questions about how societies balance protection, power, and personal freedom during health emergencies. The expansion of government authority during the Great Plague, justified by the need to protect public health, established precedents that continue to shape debates about the appropriate scope of state intervention during crises. The unequal impact of both the disease and the information used to combat it also resonates with contemporary concerns about health equity and access to life-saving resources.
Top image: A dramatic scene from the Great Plague of 1665, showing death carts collecting bodies in London streets while fires burn to ward off contagion. Source: Rita Greer/Free Art License
By Gary Manners
References
McBride, K. 2026. A journal of the plague year: Samuel Pepys and the Bills of Mortality as accounting. Accounting History. Available at: https://journals.sagepub.com/doi/10.1177/10323732251410550
University of Portsmouth. 2026. New research shows how Londoners used death data to survive the plague. Available at: https://www.port.ac.uk/news-events-and-blogs/news/new-research-shows-how-londoners-used-death-data-to-survive-the-plague
