Since the Carolingian age Catholic Christianity had spread from its heartland in the British Isles, France, the empire, Italy and northern Spain, to become the official religion of Bohemia, Poland and Hungary. A uniform though sparse church organisation existed throughout this huge area. The Christian west was divided into dioceses, though they varied considerably in size; but the provision of parishes was very uneven. All towns had at least one church while some had more than a hundred, but even in parts of the west which had been Christian for centuries many rural areas, were still served by the clergy of a central minster. The growth of parishes increased the possibility of conflict between clergy and laity. The cost of maintaining churches and priests was largely met from tithes, theoretically levied on all sources of income, but normally on the principal grain crops, but tithes were frequently impropriated by lay patrons, and this was a source of litigation.