of Wales starts in the 19th century when South Wales became heavily industrialised with ironworks; this, along with the spread of coal mining to the Cynon and Rhondda valleys from the 1840s, led to an increase in population. The social effects of industrialisation resulted in armed uprisings against the mainly English owners. Socialism developed in South Wales in the latter part of the century, accompanied by the increasing politicisation of religious Nonconformism. The first Labour MP, Keir Hardie, was elected as a junior member for the Welsh constituency of Merthyr Tydfil and Aberdare in 1900. The first decade of the 20th century was the period of the coal boom in South Wales when population growth exceeded 20 per cent. Demographic changes affected the language frontier; the proportion of Welsh speakers in the Rhondda valley fell from 64 per cent in 1901 to 55 per cent ten years later, and similar trends were evident elsewhere in South Wales. The population of Wales doubled from 587,000 in 1801 to 1,163,000 in 1851 and had reached 2,421,000 by 1911. Most of the increase came in the coal mining districts especially Glamorganshire, which grew from 71,000 in 1801 to 232,000 in 1851 and 1,122,000 in 1911. Part of this increase can be attributed to the demographic transition seen in most industrialising countries during the Industrial Revolution, as death rates dropped and birth rates remained steady. However, there was also a large-scale migration of people into Wales during the industrial revolution. The English were the most numerous group, but there were also considerable numbers of Irish and smaller numbers of other ethnic groups, including Italians, migrated to South Wales. Wales received other immigrants from various parts of the British Commonwealth of Nations in the 20th century, and African-Caribbean and Asian communities add to the ethnocultural mix, particularly in urban Wales. Kenneth O. Morgan argues that: 20th century The 1904–1905 Welsh Revival was the largest full-scale Christian revival of Wales of the 20th century. It is believed that at least 100,000 people became Christians during the 1904–1905 revival, but despite this it did not put a stop to the gradual decline of Christianity in Wales, only holding it back slightly. The world wars and interwar period were hard times for Wales, in terms of the faltering economy of antiwar losses. Men eagerly volunteered for war service. The First World War and its aftermath had severe impact