"The 1870s saw massive emigration to the United States and Canada due not only to the boom in these countries but also to the slow pace and alienating conditions of industrial development and employment in Hungary. On average, for the the half century preceding the Great War, some 30,000 people emigrated annually. Often the departure was short-term to make money in order to purchase property back home later, and a third of the emigrants throughout this period are deemed to have returned." Stanislav J. Kirschbaum, A History of Slovakia: The Struggle for Survival, 2nd edition, p. 152.
50 years (1864-1914) x 30,000 = 1,500,000 of whom 1/3 returned, or ca. 500,000 returned, leaving 1,000,000 or so Slovaks who came to this country and Canada.
"Population statistics show that in 1869, there were 1,818,228 Slovaks in Hungary (in Slovakia around 1,570,000). In 1900, that number rose to 2,008,744 (1,684,681 in Slovakia). [Ibid, p. 153]
By the year 1900, there were roughly 2,000,000 Slovaks in the Hungarian kingdom. But we know that beginning in 1864 (or so), 30,000 a year on average were leaving, with 1/3 returning (on average). So by 1900, 720,000 Slovaks had left permanently. That would be 26.5% of the entire population that left. So, that's 1 out of every four persons. Put another way, 77 million Americans would have to up and leave this country within the next 36 years for a comparable exodus.