From the Act of Union on 1 January 1801, until 6 December 1922, the island of Ireland was part of the United Kingdom of Great Britain and Ireland. During the Great Famine, from 1845 to 1849, the island's population of over 8 million fell by 30%. One million Irish died of starvation and/or disease and another 1.5 million emigrated, mostly to the United States. This set the pattern of emigration for the century to come, resulting in a constant population decline up to the 1960s.
Question: How many years did it take for Ireland's population to fall by 30%?
Answer: 4