The influence of jizya on conversion has been a subject of scholarly debate. Julius Wellhausen held that the poll tax amounted to so little that exemption from it did not constitute sufficient economic motive for conversion. Similarly, Thomas Arnold states that jizya was "too moderate" to constitute a burden, "seeing that it released them from the compulsory military service that was incumbent on their Muslim fellow subjects." He further adds that converts escaping taxation would have to pay the legal alms, zakat, that is annually levied on most kinds of movable and immovable property. Other early 20th century scholars suggested that non-Muslims converted to Islam "en masse" in order to escape the poll tax, but this theory has been challenged by more recent research. Daniel Dennett has shown that other factors, such as desire to retain social status, had greater influence on this choice in the early Islamic period. According to Halil İnalcık, the wish to avoid paying the jizya was an important incentive for conversion to Islam in the Balkans, though Anton Minkov has argued that it was only one among several motivating factors.