The bureau calculated and cross-referenced lifetime earnings for each major and each career field by grouping survey respondents into eight age buckets consisting of five years, determined the median annual earnings for each age group, multiplied the number by five, and added the totals together.
Islamists from Hamas and Islamic Jihad are included, but the grouping is led by Tanzim, Fatah's own field organisation, and militias within it, such as the al-Aqsa Brigades.