Scotland a territorial parish structure, with every community in Scotland having a local congregation. Scotland also has a significant Roman Catholic population, 19% professing that faith, particularly in Greater Glasgow and the north-west. After the Reformation, Roman Catholicism in Scotland continued in the Highlands and some western islands like Uist and Barra, and it was strengthened during the 19th century by immigration from Ireland. Other Christian denominations in Scotland include the Free Church of Scotland, and various other Presbyterian offshoots. Scotland's third largest church is the Scottish Episcopal Church. Islam is the largest non-Christian religion (estimated at around 75,000, which is
Scotland in the Middle Ages and industry remained relatively undeveloped before the end of the Middle Ages and, although there were extensive trading networks based in Scotland, while the Scots exported largely raw materials, they imported increasing quantities of luxury goods, resulting in a bullion shortage and perhaps helping to create a financial crisis in the fifteenth century. There are almost no written sources from which to re-construct the demography of early Medieval Scotland. Estimates have been made of a population of 10,000 inhabitants in Dál Riata and 80–100,000 for Pictland. It is likely that the 5th and 6th centuries saw higher mortality rates due