Norman Stillman writes that although the tax burden of the Jews under early Islamic rule was comparable to that under previous rulers, Christians of the Byzantine Empire (though not Christians of the Persian empire, whose status was similar to that of the Jews) and Zoroastrians of Iran shouldered a considerably heavier burden in the immediate aftermath of the Arab conquests. He writes that escape from oppressive taxation and social inferiority was a "great inducement" to conversion and flight from villages to Arab garrison towns, and many converts to Islam "were sorely disappointed when they discovered that they were not to be permitted to go from being tribute bearers to pension receivers by the ruling Arab military elite," before their numbers forced an overhaul of the economic system in the 8th century.