The Zoroastrian priesthood is hereditary and strictly patrilineal: only a man born into a priestly family, an athornan, can be ordained, which means that however qualified or devout, a layman cannot become a priest. Ordination proceeds in two grades, navar and martab, and requires years of memorising Avestan liturgy; the higher grade permits performance of the inner ceremonies including the Yasna, and requires the nine-night barashnum purification. In a community whose total population is under 150,000 and falling, a closed recruitment pool is an arithmetic problem, and it has become acute: the number of practising full-time mobeds in India is now counted in the low hundreds, many are elderly, and priesthood is poorly paid relative to the professions Parsi families otherwise enter. Fire temples in Gujarat have closed for want of a priest. Diaspora communities frequently rely on visiting priests or on part-time mobeds with other careers, and North American associations have trained and authorised mobedyars, lay assistants permitted to perform outer ceremonies, which the Indian priesthood does not recognise.