Ireland; Population in 1841 was 8,175,124
Ireland; Population in 1911 was 3,139,688 ((N.I)1,250,531)
The 1841 figures omit up to 2,000,000 living in the most remote bogland and mountainous regions not reached by British census takers.
Scotland; 1841 population, 2,620,184
Wales Population, 1841, 1,045,958
Wales Population, 1911, 2,420,921
Irish Census Records as a dominion of Great Britain throughout the 19th Century are either incomplete or destroyed.
The original census returns for 1861 and 1871 were destroyed shortly after the censuses were taken. In Mainland UK the same census records survive, transcriptions having first been taken before the records destruction.
Those for 1881 and 1891 were pulped without transcription during the First World War. The same records on mainland Britain survive, transcriptions having been made. The returns for 1821, 1831, 1841 and 1851 were destroyed during shelling of the Public Record Office in the Civil War, a handful of records survive for a few counties for 1821 and 1831.
An article from Guardian Newspaper regarding a former colony, Kenya states; secretary of state for the colonies talked about the destruction of records, directed that post-independence governments should not get any material that “might embarrass Her Majesty’s government”, that could “embarrass members of the police, military forces, public servants or others eg police informers”, that might compromise intelligence sources, or that might “be used unethically by ministers in the successor government”.