This year will be the eleventh edition of the Global Terrorism Index (GTI). The report provides a comprehensive summary of the key global trends and patterns in terrorism over the last decade. The calculation of the GTI score considers not only deaths but also incidents, hostages and injuries from terrorism, weighted over a five-year period. The report is produced using event records on terrorist attacks since 1 January 2007. The current terrorism dataset contains over 66,000 terrorist incidents for the period 2007 until today.

The GTI ranks 163 countries based on four indicators weighted over five years. A country’s annual GTI score is based on a unique scoring system to account for the relative impact of incidents in the year. The four factors counted in each country’s yearly score are:

• a total number of terrorist incidents in a given year
• a total number of fatalities caused by terrorists in a
given year
• a total number of injuries caused by terrorists in a
given year
• a total number of hostages caused by terrorists in a
given year

Each of the factors is weighted between zero and three, and a
five year weighted average is applied in a bid to reflect the
latent psychological effect of terrorist acts over time. The
weightings shown in Table C.1 were determined through
consultation with the GPI Expert Panel. The greatest weighting is attributed to a fatality.