 The population of Ireland collapsed dramatically during the second half of the 19th century . A population of over 8 million in 1841 was reduced to slightly more than 4 million by 1921 . In part , the fall in population was due to death from the Great Famine of 1845 to 1852 , which took about 1 million lives . However , by far the greater cause of population decline was the dire economic state of the country which led to an entrenched culture of emigration lasting until the 21st century . 
