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The London Cholera Attack of 1854: How did this plague become the most famous natural experiment in history?
In 1854, a cholera epidemic broke out in London, which became a classic natural experiment. This epidemic is not just a spread of disease, but also reveals the close connection between public health and environmental factors. Through this example, scientist John Snow used observation and map analysis to successfully find the water source of cholera. This discovery came from an undesigned experiment. The hub of the infection revolved around a water pump, furthering the push for health reform.
John Snow discovered that the incidence of cholera was significantly correlated with the water provided by the pumps, an unprecedented connection at the time.
The 1854 cholera epidemic broke out in London's Soho district. In just three days, 127 people died of the plague, and 616 people eventually died. Snow's investigation and analysis highlighted the quality of water sources, particularly the area's water suppliers, Southwark and Vauxhall Waterworks Company, which sourced water from the polluted Thames.
Snow cited the chaotic state of London's water supply at the time and described it as a "grand experiment".
This incident revealed the huge impact of environmental pollution on public health and prompted the London City Council to embark on comprehensive sanitation reforms to improve the water system. At that time, many water sources were supplied to the general public without even being properly treated, making people aware of the direct impact of water quality on health.
The cholera incident not only demonstrated the power of natural experiments at the time, but also promoted the progress of epidemiology in subsequent scientific research, especially in the field of public health. Snow's research methods inspired many scientists to conduct similar studies in the future. This epidemic is definitely an experiment taking place under natural conditions.
In addition to the impact of the cholera incident, what other modern cases have become important natural experiments?
Of course, cholera is not the only case. In modern times, scientists still rely on natural experiments to study a variety of phenomena. These include the impact of family size on mothers’ workplace outcomes, research on the economic behavior of creative game shows, and more. These studies demonstrate the importance of natural experiments in various fields.
The impact of family size
For example, researchers Angrist and Evans examined how family size affects mothers' workplace outcomes in a 1998 study. The gender of the first two children in a family can become a "natural experiment," research has found, further revealing the impact of having a third child on a mother's earnings. These results provide a deeper understanding of the association between family structure and workplace experiences.
Research on game shows
Another interesting example is the study of game shows conducted in economics. Although game shows appear to be nothing more than contrived, they can actually be viewed as natural experiments to study people's decision-making behavior in risky environments. Game shows provide an intervention-free environment that allows researchers to observe participants' reactions in different situations.
Impact of smoking ban
In Helena, Montana, a 2002 ban on smoking in public spaces led to a 40% drop in heart attack rates within six months. After the ban ended, heart attack rates rose again. This opened up in-depth research on the effects of public health policies, showing that smoking bans also have the characteristics of natural experiments in living environments.
Vietnam War Recruitment Policy
The draft policy during the Vietnam War also provided a rare natural experiment. Researchers Angrist used the draft lottery system to compare the difference in lifetime earnings between drafted soldiers and those who were not drafted. The results showed that the average income of veterans was about 15% lower than that of non-veterans.
Industrial blackening phenomenon
So many examples, both natural and social, demonstrate the value of natural experiments. Historians and scientists have gained important insights from these studies and have followed the resulting changes.
From the cholera incident in London in 1854 to various natural experiments today, these forms of research not only provide us with a deeper understanding of the workings of human society, but also inspire endless possibilities for future research. Can we learn from the lessons of history to explore more natural experiments in the future?
