Between 1825 and 1925, 800,000 Norwegians came to the U.S., mostly settling in the Midwest. The mid-19th century was an especially good time to leave Norway. Indeed, at the time, some might have called it “a shithole.” Unemployment was high, there was little social mobility, and there wasn’t enough land for farms. The United States had recently passed the Homestead Act (1862), which gave settlers free land as long as they stayed on it for at least five years. The allure proved so great that Norway is estimated to have lost a larger share of its population to the U.S. than any other country, save Ireland. That was until the passage of the 1924 Immigration Act, the law designed to keep out Southern and Eastern Europeans, and Asians. The law had one unintended consequence: It dramatically lowered immigration from northern European Norway.

There’s little evidence to suggest that Norwegians, because they are overwhelmingly white, had an easier time assimilating in the U.S. during the period of mass migration that ended with the Immigration Act of 1924.

“Norwegian immigrants did so poorly in the United States that about 70 percent of them returned & stayed in Norway,” Alex Nowrasteh, an immigration-policy analyst with the Cato Institute, wrote Thursday on Twitter. “Return rates are not always a sign of failure but their low wages, despite observable characteristics, and poor 2nd generation assimilation indicate otherwise here.” (You can find the historical data on migrants who returned to their home countries here.)

A 2013 working paper from the National Bureau of Economic Research noted that wages for first- and second-generation Norwegians were lower than any other immigrant group in that period of mass immigration, except those from Portugal.

After World War II, immigration to the U.S. increased again, as veterans returned home with their foreign-born wives. In the 1950s and ’60s, Norwegian immigration rose again (22,806 in the 1950s; 17,371 in the ’60s). But the 1970s saw a sudden slide (3,927). The levels of Norwegian immigration have hovered at that level in the decades since then. What changed? Norway did.

The country discovered oil in the late 1960s, and, unlike other resource-rich countries that have succumbed to mismanagement and corruption in the face of sudden wealth, invested heavily in its people and its economy to become one of the world’s wealthiest places. Its per capita gross domestic product went from $1,441.80 in 1960 to $70,911.8 now, according to World Bank data. (The U.S. figure is $57,638.20.) Norway has higher life expectancy at birth than the U.S., lower rates of infant mortality, low unemployment, and access to the European Union’s labor market (though it’s not an EU member).

Additionally, Norway is the world’s happiest country (the U.S. ranks 14), the place with the most political freedom (the U.S. ranks 45), most press freedom (the U.S. ranks 43rd), and most prosperity (the U.S. ranks 18). Simply put, there’s little economic incentive for Norwegians to immigrate to the U.S.