There are about 6.5 million people in the Republic of Ireland and Northern Ireland combined. How did such a small island produce something like 50 million people of Irish descent in the US and 14 million in the UK. Even countries like Australia and Canada have more people of Irish ancestry than Ireland itself.
Most Western European diaspora populations are similar in numbers to the population in their ancestral homeland, but Ireland's diaspora is something like 7 times larger than Ireland's population.
Is this due to unusually large fertility rates among Irish immigrants in other countries? Or did Ireland already have a larger population than other European countries, but most just left?
That's because Ireland actually hasn't recovered demographically since the Great Famine in the 1840s and 50s. On the eve of the famine, Ireland's population hovered between 8 and 9 million, the majority of which were impoverished tenant farmers or bothach ("hut-dweller") who had been living in a state approximating apartheid until 1829 and the repeal of the Penal Laws.
It's estimated that around one million Irish people died during the famine while another million emigrated abroad, however emigration would continue throughout the century and into the 20th century. Essentially, even if you weren't forced to flee Ireland because of famine or political repression, it wasn't a very nice place to live for the majority of the impoverished Catholic population who might find actual employment or be able to establish their own farms in Canada, the US, England, Australia etc.
