Terrorism by the Numbers

Posted on May 1, 2016

Contributed by Ismael Jaime Cruz. He  is currently in the NYC Data Science Academy 12 week full time Data Science Bootcamp program taking place between April 11th to July 1st, 2016. This post is based on his first class project - R visualization (due on the 2nd week of the program).


Over the past year, terrorist incidents have been growing by the numbers with attacks hitting different regions including Europe, Africa, and the Middle East. In November 2015, Paris was hit by the Islamic State and produced a death toll of at least 130, stirring sympathy and outrage from the global community. In other areas such as Nigeria, casualties from terrorist attacks were estimated to have been in the thousands.

Last December 2015, a Gallup survey showed that terrorism was the most pressing issue for Americans. It stated that one in six Americans believed terrorism was the most important U.S. problem, the highest figure in a decade and edging out other issues such as the economy and government.

Gallup Survey conducted December 2-6, 2015

In light of these terrible incidents, I wanted to see how terrorism has been changing over the years and how it has affected different areas around the world.

I set out to do the analysis through an exploration of the Global Terrorism Database (GTD) provided by the National Consortium for the Study of Terrorism and Responses to Terrorism (START).

Background of GTD

  • A highly comprehensive and consistent terrorism incident dataset from 1970 to 2014
  • Data collection methodology consists of a combination of automated and manual data collection strategies of over a million media articles worldwide
  • Filtered using natural language processing and machine learning techniques
  • Terrorism incidents from 1993 are missing due to lost data prior to START's compilation of the GTD from multiple data collection efforts

Terrorism Statistics

The GTD includes almost 142,000 incidents of terrorism from 1970 to 2014. On average, there have been 3,227 attacks per year with about 7,046 casualties a year.

Attacks by Year

  • The number of attacks looks to have fallen in the 1990s and then increased beginning 2005
  • The growth of the number of attacks in recent years is alarming, more than tripling from 2011 to 2014

Types of Attacks

  • Almost half of all attacks were of the bombing/explosion type
  • Followed by armed assault and assassination at 24% and 12%, respectively

Attack Type by Year

I wanted to see how the top 3 most common attack types changed over time.

  • Assassinations looked to have dropped significantly in the late 1990s
  • The increase in bombings in recent years is startling
  • Bombings look to have severely outpace armed assault after the year 2005

Casualties by Year

Next, apart from the incidents of terrorism, I thought it was also important to see the gravity of the attacks in terms of casualties.

  • Very similar to the attacks by year
  • Not surprisingly, the correlation between casualties and attacks is 0.94

Casualties from Attack Type by Year

  • Here indicates a turning point wherein armed assault claimed majority of casualties prior to the year 2003
  • After which, bombings began to claim more casualties

Terrorism Attacks Globally

At this point I wanted to compare what terrorism looked like from different areas around the world. I decided to tally attacks in major global cities and compare them to the top cities by frequency of attacks. I defined major global cities to be the list of 16 Elite Global Cities as described by the management consulting firm A.T. Kearney. According to the firm, such cities are hubs of commerce, culture, and politics and are likely to exert their global influence well into the future. The other group consisted of the top 16 cities with the most attacks which include cities from South Asia, South America, and the Middle East.

Global Elite Cities

Top 16 Cities by

Frequency of Attacks


New York City


Los Angeles






San Francisco



San Salvador


















Guatemala City



Attacks in Global Elite Cities vs T16


  • Majority of attacks for the global elite group were from 1970 to 1992 and tapered off thereafter
  • Attacks in the T16 group began increasing beginning 2003
  • On average, the global elite group experienced 49 attacks per year while the T16 group experienced 555 attacks per year

Casualties in Global Elite Cities vs T16

  • There is a disparity in terms of casualties and attacks for the global elite group since casualties were quite low all throughout except for a few years
  • The spike in casualties in the elite group in 2001 was due to the 9/11 attack in the U.S. where more than 2,700 people died
  • On average, the global elite group experienced 87 casualties a year while the T16 group experienced above 9 times more at 809 casualties a year


Terrorism is an important issue that different regions across the world are facing. It is alarming that the number of terrorist attacks have been surging in recent years primarily led by bombings. Although it may be a good indication that the casualties from armed assault have more or less decreased over the years, it is frightening to see that bombings have taken the lead as the primary cause of casualties in the last decade. In addition, despite terrorism occurring in different parts of the globe, the difference in terms of attacks and casualties across major global cities and regions such as the Middle East and South Asia are too significant to go unnoticed.

Questions for Future Analysis

Some questions I would like to explore for future analysis:

  1. Were there certain countries that only started experiencing terrorism incidents recently?
  2. What were the causes behind the surge in number of attacks?
  3. Why did bombings start to claim more casualties?
  4. What global regions experienced an increase/decrease in terrorism?


Code for the graphs above:

About Author

Ismael Jaime Cruz

Ismael’s roots are in finance and statistics. He has six years of experience in such areas as financial analysis, trading and portfolio management. He was part of the team that launched the very first exchange-traded-fund in the Philippines....
View all posts by Ismael Jaime Cruz >

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