Cumulative Percentage of Preparatory Acts Over Time

For each case study, researchers analyzed when terrorist groups performed preparatory acts that led to the attacks. They learned that international terrorists typically began their preparations 3+ years before an attack; right-wing terrorists at one to three years; environmental terrorists at four to six months; and left-wing terrorists at one to three months. The cumulative percentages of the acts for each group are as follows:

International Terrorists. By the day of the incident, international terrorists had completed all but five percent of their preparatory acts; by the day before the incident, they had completed all but nine percent; by two to three days before, they had completed all but 13 percent; by four to seven days before, they had completed all but 21 percent; by eight to 14 days before, they had completed all but 32 percent; by 15 to 30 days before, they had completed all but 55 percent; within one to three months of the incident, they still had 68 percent of their preparatory acts to complete; within four to six months, they still had 84 percent to complete; at seven to 12 months, they had 89 percent to complete; between one and three years, they had 97 percent to complete; and at 3+ years, 100 percent of their preparatory acts were not yet completed.

Right-Wing Terrorists. By the day of the incident, right-wing terrorists had completed all but 15 percent of their preparatory acts; by the day before the incident, they had completed all but 26 percent; by two to three days before, they had completed all but 31 percent; by four to seven days before, they had completed all but 44 percent; by eight to 14 days before, they had completed all but 49 percent; at 15 to 30 days before the incident, they still had 67 percent of their preparatory acts to complete; within one to three months, they had 94 percent to complete; at four to six months and seven to 12 months, they had 96 percent to complete; and between one and three years, 100 percent of the preparatory acts were not yet completed.

Environmental Terrorists. By the day of the incident, environmental terrorists had completed all but 20 percent of their preparatory acts; by the day before the incident, they had completed all but 43 percent; at two to three days before, they still had 72 percent of their preparatory acts to complete; at four to seven days before, they still had 80 percent to complete; at eight to 14 days before, they had 91 percent to complete; at 15 to 30 days before, they had 95 percent to complete; within one to three months, they had 98 percent to complete; and within four to six months, 100 percent of their preparatory acts were not yet completed.

Left-Wing Terrorists. By the day of the incident, left-wing terrorists had completed all but 50 percent of their preparatory acts; on the day before the incident, they still had 75 percent of the acts to complete; at two to three days, four to seven days, eight to 14 days and 15 to 30 days before, they had 88 percent to complete; and within one to three months, 100 percent of their preparatory acts were not yet completed.

All Terrorists. By the day of the incident, all terrorists had completed all but 13 percent of their preparatory acts; by the day before the incident, they had completed all but 27 percent; by two to three days before, they had completed all but 40 percent; by four to seven days before, they had completed all but 48 percent; by eight to 14 days before, they had completed all but 57 percent; at 15 to 30 days before the incident, they still had 72 percent of their preparatory acts to complete; within one to three months, they still had 85 percent of their preparatory acts to complete; within four to six months, they had 93 percent to complete; at seven to 12 months, they had 95 percent to complete; between one and three years, they had 99 percent to complete; and at 3+ years, 100 percent of their preparatory acts were not yet completed.