In "The Baha'i Faith 1957–1988: A Survey of Contemporary Developments" ("Religion": 1989), Baháʼí authors Momen and Smith provide the following estimates of the Baháʼís in the world over 3 decades, broken out by cultural areas. They derived numbers from, "calculation of approximate numbers from the number of Bahá'í organizations; extrapolating back from the official figures for the number of individual Bahá'ís provided more recently; estimates provided by informed Bahá'ís; and when the first draft of this paper was completed, a copy was sent to the Department of Statistics in Haifa and the present table incorporates some of the statistical information given in the reply to this, dated 8 July 1988."