The title "Why Have We Not Been Attacked Again? Competing and Complementary Hypotheses for Homeland Attack Frequency" is rather odd IMO.

I assume the paper refers to successful attacks on the USA homeland, so where is the assessment of thwarted plots? Plots that have resulted in successful crininal prosecutions, not media hyped stories after official leaks.

I am not immersed in 9/11, but could it be seen as a carefully planned attack, that had a perceived - by AQ - as having a high risk of pre-attack disruption / failure? We now know that the plotters preparations were "dots not joined up" by intelligence and law enforcement (I do not fully share that "dots" explanation).

Post-9/11 AQ attacks display a mixture of independent action ranging to centrally directed action. That suggests that an attack on the USA could originate from a variety of directions, possibly without a full risk assessment.

davidbfpo