An index nearly always has an implicit tension. The aim is to create a simple measure of a complex phenomenon: that is anything but simple. The aim of the Global Peace Index is to take something as complex as peace and to simplify it into a definable and measurable phenomenon.
The first step towards doing it well is to have a robust definition of what is to be measured. For example, if you say, ‘I want to measure good government’, then you have created a myriad of problems around the word ‘good’.
With peace, if you get your definition wrong, or worse still, start measuring things without a clear idea of why you are measuring, the outcome will inevitably be amorphous.
Otherwise, measurement becomes problematic. All too often, indexes do not have clear definitions of what they are measuring, which leaves them open to criticism of subjectivity or leads to ambiguous outcomes.
One way of understanding the robustness of an index is to see whether the organisation fully publishes its methodology. If the methodology is not published, then more than likely it is flawed.
This can be particularly challenging when compiling and normalising global data. To overcome this, the Index uses a combination of quantitative and qualitative indicators, the latter compiled and weighted by experts.
This provides multiple perspectives and contributes to a more robust index.
An excellent example of this is the terrorism indicator. This was originally scored by the Economist Intelligence Unit as an expert score called the Likelihood of a Terrorist Attack.
Over time we found that it lacked reliability because of the difficulty in predicting black swan terrorist events.
However, the University of Maryland started a large project, partly funded by the US government, to compile a database of terrorist attacks by scouring global news sources for reports.
So, rather than being a projection of the likelihood of terrorism, it became a measure of terrorist activity in the preceding year, which is more accurate and more appropriate for an annual index.
In time this new measure led to another index, the Global Terrorism Index, which has now become a major product. It has taken on a life of its own and is used by major intelligence organisations around the world as a key source in their fight against terrorism.
Each indictor in the Global Peace Index is weighted according to the effect it has on society. While homicides have more impact than fear of violence, determining the correct value of the weight is crucial.
There are statistical techniques to come up with weightings, but they have their flaws. We decided to use an expert panel to reach a consensus on the relative importance of each indicator.
Our definition of peace as the ‘Absence of violence or fear of violence’, and the fact that the 23 indicators in the Index are designed to be clearly differentiated from each other, makes us confident that the Global Peace Index is not a proxy measure of something else, such as per capita income.