The War on the Rocks website recently took a studied look at the number of terrorist attacks before and after 9/11, both inside and outside warzones. The thought-provoking study paired the Global Terrorism Database from the University of Maryland with civil war and insurgency data from the Uppsala Conflict Data Program in 194 countries. Spanning the years 1989 to 2014 allowed it to directly compare terrorist attacks in the early post-Cold War era with those since 2001.

It reports that the graphic indicates that global terrorist attacks rose dramatically after 2004: there were just over 1,000 in 2004, but almost 17,000 in 2014. The numbers from 2015 and 2016 (not shown) have remained remarkably high, but below the 2014 peak. The upward pattern holds even when removing attacks in Iraq and Afghanistan. However, it notes that more than 70% of the attacks in the past 10 years transpired in just 2 regions, both of which have seen extensive insurgency and civil conflict during that time: North Africa/Middle East and South-Central Asia. The article then posed the question, what do the numbers of attacks look like outside of places beset with civil strife?

The article highlights conclusions made from the data, including the apparent oddity that perhaps counterintuitively, the graphic also indicates that for a period in the mid-1990s, terrorist attacks in countries not experiencing civil wars exceeded attacks in war-torn states.
The article draws a number of significant conclusions – firstly, it is possible that post-9/11 counter-terrorism efforts have contributed to reducing incidents of non-insurgency terror (plus providing “easier” and more tempting targets in war zones, namely US and other soldiers in Afghanistan etc). Secondly, the decline in terrorism it describes could be reversed in the next several years (for example, if returning fighters caused mayhem).
Finally, and perhaps more importantly in a Trump era, the evidence raises difficult questions about the efficacy of the US approach to the war on terror in the future. Is it willing to maintain a sustained presence in Afghanistan, the Middle East, and parts of Africa to confront a problem that is increasingly regional and local?
The article makes some further observations (including civil wars are not normally the result of terrorism, but that terrorists exploit the conflict) and recommendations for US policy.
https://warontherocks.com/2017/12/terrorism-war-terror-look-numbers/