Those arguing for more profiling quite frequently claim that while not all Muslims are terrorists, most terrorists are muslim. Is there data to show that more than 50% of terrorists attacks can be attributed to any one religious or political affiliation.
To clarify some.
Terrorism : The use of violence, outside of war, to manipulate or coerce a population.
Region : US and Europe
The answer to this question varies greatly, depending on country you are from.
If you're from the Netherlands, Islamists represented 100% of the individuals suspected of terrorism each year from 2006 to 2009 (between 2 or 6 per year), except in 2007. On the other hand, if you are from France, then, while Islamists do represent a sizable number of the arrested suspects, the percentage is far lower (342 out of 1468, or 23.2%) in the same timespan.
In the United States, more than 80% (186 out of 228) of all convictions tied to international terrorist groups since 9/11 involve defendants driven by a radical Islamist agenda.
The European Union has a graph of arrested terrorism suspects by Member State in its Terrorism Situation and Trend Report 2010:
It also states that:
The number of arrests relating to Islamist terrorism (110) decreased by 41 % compared to 2008, which continues the trend of a steady decrease since 2006.
Since you're interested in those numbers to discuss more profiling, arrested suspects are not what is interesting to look at. Instead, that would be successful attempts.
There are few successful attempts, at least in Europe, over the last few years. For example, there was only one attempt in 2009:
The preceding years are not very different. In the recent years, Islamist terrorism has not been very successful. For example, the Terrorism Situation and Trend Report 2008, which reports on terrorism in the European Union in 2007, states that:
With regard to Islamist terrorism, two failed and two attempted attacks were reported for 2007. As in 2006, failed or attempted Islamist terrorist attacks took place in the UK, Denmark and Germany. Police investigations into the attempted attacks in Denmark and Germany have shown that the intended targets were likely to be located on their national territory.
However, as the report notes, "The failed and attempted attacks mainly aimed at causing indiscriminate mass casualties." As such, even one successful attack can lead to a large amount of causalities.
- Terrorism Situation and Trend Report 2007
- Terrorism Situation and Trend Report 2008
- Terrorism Situation and Trend Report 2009
- Terrorism Situation and Trend Report 2010