Complex sentence: According to B'Tselem, there was a decline, starting in 1998, in the number of Palestinians held in administrative detention where, on average, less than 20 were held from 1999 to October 2001.
Split into simpler sentences: According to B'Tselem, there was a decline, starting in 1998, in the number of Palestinians held in administrative detention. Less than 20 were held from 1999 to October 2001.