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READ: Data Exploration - War and Peace

The past was not peaceful. Is there more violent conflict today than in the past? Is war becoming deadlier? The data is more complicated than you might think.
The data exploration article below uses “Three Close Reads”. If you want to learn more about this strategy, click here.

First read: preview – what do we have?

This will be your quickest read. It should help you get the general idea of what this chart is about and the information it contains. Pay attention to:
  • Labels and titles. What is the title? How are the axes labeled? Is anything else on the chart labeled?
  • Data representation. How many variables are there and what are they? What are the scales? What time period does the chart cover? Is the chart interactive?
  • Data source. Where did the data for this chart come from? Do you trust it? Who created the chart?

Second read: key ideas – what do we know?

In this read, you will pay attention to the information that most helps you understand the chart and the information it is trying to convey. Pay attention to:
  • Claim(s). What can you say about the data? What story does it tell? Can you make any claims about this data? Does it change when you zoom in compared to when you look at the data as a whole?
  • Evidence. What data from the chart supports this story? Does this change if you change the scale or variables?
  • Presentation. How does the way this chart is presented influence how you read it? Has the author selected certain variables or scales that change the conclusions that can be drawn? Is there anything missing from this chart?
By the end of the second read, you should be able to answer the following questions:
  1. How are Charts 1 and 2 different? How are they similar?
  2. What does Chart 1 tell us about war in the last 500 years? Do you think measuring war between the great powers is a good way to understand war in general?
  3. What does Chart 2 tell us about how the deadliness of conflict changed during the twentieth century?
  4. According to Chart 3, what was the deadliest event in human history?
  5. Charts 1 and 2 suggest that the frequency and deadliness of conflict might be declining, especially during the twentieth century. Why does Chart 3 show so many more conflicts in recent centuries than earlier in history?

Third read: making connections – what does this tell us?

The third reading is really about why the chart is important and what it can tell us about the past and help us think about the future. Pay attention to:
  • Significance. Why does this matter? Does this impact me, and if so, how? How does it connect what is going on in the world right now? How does it relate to what was happening at the time it was created?
  • Back to the future. How does this data compare to today? Based on what you now know, what are your thoughts on this phenomenon 25 years, 50 years, and 100 years from now?
At the end of the third read, you should be able to respond to these questions:
  1. These three charts use similar data to tell slightly different stories. Which do you trust the most to tell us something important about deadly conflict? Why?
  2. Using these three charts, make one prediction about the future of warfare and deadly conflict in your lifetime. What evidence from the charts supports your prediction? What evidence challenges it?
Now that you know what to look for, it’s time to read! Remember to return to these questions once you’ve finished reading.

War and Peace Data Introduction

Bleak photo of a modern, low-tech soldier walking alone in an area completely destroyed by war.
By Max Roser, adapted by Eman M. Elshaikh
The past was not peaceful. Is there more violent conflict today than in the past? Is war becoming deadlier? The data is more complicated than you might think.


The past was not peaceful. Human history has been a story of conquest as much as it has been a story of peace. But many people have the idea that human history only became more violent recently. One reason why some people might have this impression is that people alive today don't remember these conflicts. They are simply forgotten. We also have incomplete information to help remind us. Our data about historical conflicts is not perfectly accurate, but we do have some evidence that helps us estimate the number of fatalities. The visualizations below will give you a sense of these estimates.
Chart 1:
Percentage varies from 70 percent to 100 percent for two centuries, then begin to drop in the mid 1700s. By 2000, the percentage drops to zero.
We think of recent wars—and especially the world wars of the twentieth century—as the deadliest conflicts in human history. In fact, however, there were many, many wars for land, power, and ideology that occurred long before the twentieth century. Some people argue that war has actually become less common in the last century than in previous centuries. Chart 1 shows the percentage of years the "great powers" fought each other, beginning in 1500 CE. "Great powers" are those states that are (or were) militarily or economically powerful on a global scale.

More wars or more peace?

Chart 1 seems to indicate that wars have become less common over time. But is that the whole story, or is it more complicated? To understand the role of conflict today relative to wars of the past, we can look at long-term data. Chart 2 shows deaths from global conflicts over the past 600 years or so, beginning around 1400. This helps us better understand whether humanity is trending toward more or fewer conflicts, and more-deadly or less-deadly wars. The x-axis of this chart represents time, from about 1400 CE to the present. The y-axis represents the number of people killed in war per 100,000 people in the world.
Chart 2:
Complex chart using bubbles and lines to show the number of deaths around the world caused by war between the years 1400 and 2000.
Explore at: https://slides.ourworldindata.org/war-and-violence/#/6 By Our World in Data, CC BY 4.0.
The red circles visualize the conflicts listed in the "Conflict Catalog," by Dr. Peter Brecke. Brecke's data set contains information on 3,708 conflicts. For the more distant past, Brecke lacks an estimate of the number of fatalities for many of the conflicts he catalogs, and we suspect that many conflicts are completely unknown. Since the global population has changed a lot over the last 600 years, Chart 2 also provides data about the percentage of the global population that decreased as a result of these events. This will help you get a sense of how impactful these events were at the time. In addition to the individual conflicts, the chart shows an estimate of the average death rate (deaths in conflict as a percentage of the global population) from all conflict across the globe (the red line). After about 1900, there are two different estimates—one represented by the red line, the other by the blue line.
Chart 3 is another visualization, one that depicts deaths from the 100 deadliest wars and other atrocities over the longer timeframe of the past millennia. The size of the circle indicates how many people died in the event, while the line through each circle indicates how long the conflict lasted. The color of each circle shows where each conflict occurred. When and where did the deadliest wars occur? Is the world becoming more peaceful, or more warlike? What factors might cause this trend to continue or to change?
Chart 3:
Data showing deaths from war and similar conflicts from the year 400 to 2000, including the percentage of the total world population lost in each conflict.
Author bio
Max is the founder and director of Our World in Data. He began the project in 2011 and for several years was the sole author, until receiving funding for the formation of a team. Max’s research focuses on poverty, global health, and the distribution of incomes. He is also Programme Director of the Oxford Martin Programme on Global Development at the University of Oxford, and Co-executive Director of Global Change Data Lab, the non-profit organization that publishes and maintains the website and the data tools that make OWID’s work possible.

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