It's no secret that immigration is transforming politics in the western world.

In America, Donald Trump's shockingly successful campaign has been built around the issue, and restricting immigration may rapidly become a litmus test for conservatives. In the U.K., immigration has detached the Labour Party from working class white Britons, possibly forever. On the European continent, reaction to mass immigration has caused a spiritual rift between Eastern and Western Europe's respective political classes. The issue inspires the fortunes of populist parties in Sweden and Switzerland.

There's a trend in the media to blame the rise of the issue on the demagogues stoking the flames. But what if our mental model of immigration needs updating for the world that we live in? What if immigration truly is different today than 50 years ago? Because one of the largest factors in immigration patterns worldwide is this: The financial and psychological cost of emigration is rapidly falling.

In America we are often told that mass immigration turned out fine in the past. So it must be fine in the present. Americans of an older stock were once horrified at the great wave of Irish, then Italian immigration. Their fears that the peasant-Irish immigrating to America would become a permanently impoverished class of illiterates, or promote illiberal Old World beliefs turned out to be mostly false.

But consider the material conditions at the time. The Irish notoriously came in "coffin ships," on which a startling number died during the journey. When my ancestors on my mother's side left Ireland in 1865, they and their descendants eventually lost all but a sentimental connection to their homeland. Those that came from Gaeilge-speaking parts of Ireland, like my ancestors, did not pass on their native language, even if they gave English the word "galore." Although some entertained notions of going home again, most didn't — nor did they have the means for a casual visit. They resolved to make a life in America. America also adopted an ideology of assimilating them, with the president inveighing against "hyphenated Americans." For a few generations they may have married within the community descended from Irish immigrants, but eventually they intermarried.

Rising wealth, plane travel, and global communications networks change our calculations. They lower the price of emigration, financially and emotionally. Many more people can afford to move. And emotionally, one doesn't have to give up a home country, its food, or even all of its folkways. These developments make it affordable to maintain constant interaction between diaspora and the home country. And so, many do. The Pakistani communities in Britain retain long lasting contact with Pakistan, even continuing to marry native Pakistanis for several generations.

Two-thirds of British Muslims only mix socially with other Muslims; that portion is undoubtedly higher among Pakistanis and Bangladeshis specifically. Reinforcing this parallel life is the common practice of returning "home" for a few months every two or three years and an immersion in foreign electronic media. Integration into a wider national life is further hindered — and the retention of a deeply foreign culture is further encouraged — by the fact that most Pakistani marriages, even if one spouse is born in Britain, essentially produce first-generation-immigrant children: The one study that measured this phenomenon, conducted in the north England city of Bradford, found that 85 percent of third- and fourth-generation British Pakistani babies had a parent who was born in Pakistan. (Incidentally, that study also found that 63 percent of Pakistani mothers in Bradford had married their cousins, and 37 percent had married first cousins.) [The American Conservative]

The number of migrants from the Global South to the Global North is now equal to the number of migrants within the Global South itself. One of every nine Africans with a tertiary diploma is currently living in a member state of the Organization for Economic Cooperation and Development (OECD).

The truth is that the lower price of travel and the ability to immerse oneself in foreign language media can even change previous waves of immigration. Long lost ties from previous waves of immigration can even be re-established. I've seen it in my own life. Did I mention my own father is native Irish, and may mother began speaking the Irish language 120 years after her ancestors gave it up? One of my American-born cousins spent long stretches in Ireland. I now keep in light contact with an extended family over iMessage and Instagram. I read the Irish newspapers online, and stream the foreign language television network TG Ceathair on my iPad.

Millions of people from Central and South America will do the same in the United States. Just as many Serbians do so in Germany. Not all immigrant waves stay. When the bust hit European nations, many Poles who had sought work in Western Europe returned home.

In this new model, a wave of immigration doesn't have to crest. It can establish a community that maintains itself against the national culture with astonishing tenacity, and with the help of constant recirculation of people in and out of the diaspora.

The new form of immigration is going to challenge our assumptions about integration and assimilation. The enforcement of our laws and the norms of our culture depend on shared assumptions. It used to be that time and immersion in the melting pot would create the conditions for a common culture. Maybe that's no longer true.

Just as the industrial revolution and shipping changed and upended local economies forever, so too may the cheaper movement of people change our assumptions about what a nation is.