Tag Archives: John Kennan

Migration: how many, what kind, and why it matters

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This post is an introduction to a planned series of posts (some by me, some perhaps by others) that explore questions related to how many people might move under various changes that lead towards open borders (locally or globally). The goal of the current post is to explain why I consider the question extremely important. A subsequent post will take a somewhat opposite stand: namely, try to sketch a case for open borders that is independent of how many people might move. Later posts will look at specific policy changes, some of them realistic and others less so, and estimates of what might happen under these. Another area I plan to explore is the question of what the most critical bottlenecks are to large-scale migration (the most obvious candidates are housing and infrastructure) and what limits they set on migration rates.

A while back, I wrote a blog post critical of what I called “economic determinism”: the idea that migration flows are determined completely by economic conditions and that legal barriers to migration have practically zero effect on the magnitudes of migration flows. There are factors other than economic conditions and legal barriers to consider as well, of course: factors such as cultural connections between the sending and receiving country. Alvaro Vargas Llosa’s recent book Global Crossings: Immigration, Civilization, and America drove this point home for me. So, I guess the position I am broadly critical of could be expanded beyond economic determinism to what I might call “restriction irrelevantism”: the idea that restrictions imposed by nation-state governments on migration are largely irrelevant in terms of their effect on the magnitude and nature of migration flows.

Vargas Llosa is definitely not an economic determinist, but whether or not he’s a restriction irrelevantist remains to be seen. This article seemed to suggest that he might be, but op-eds tend to be oversimplifications, and his book, which I haven’t completed reading, may offer a more nuanced picture. I was nonetheless somewhat disappointed by the fact that Chapter 3 of the book, titled “Why They Move” and otherwise excellent at considering the motivators for migration, gave short shrift to the idea that different degrees of restrictionism in different target countries might significantly affect people’s decision of whether or where to migrate.

In any case, this blog post is not about the somewhat extreme position of restriction irrelevantism, which may or may not have real proponents. The majority of proponents and opponents of open borders do not subscribe to restriction irrelevantism. Rather, I think there’d be general agreement that millions more would move, temporarily or permanently, under open borders. But “millions” is a vague term. It could range from an extra five million people over the next two decades to an extra 100 million migrants (many of them temporary) within 2-3 years of global open borders (the main data for how many would move under open borders in terms of the stated preferences of potential migrants are the polling data on migration, which suggest that over a billion people want to go to other countries temporarily or permanently, and about 500-700 million people think they would make long-term moves if they were allowed to). One could come up with a fairly diverse (albeit less so) range of estimates for the number of people who might move under a more targeted open borders regime. For instance, if the United States announced open borders for Haiti (population about 10 million), one might envision a scenario of anything between 2 million people moving to the United States over the next year to a roughly equal number moving to the United States over the next two decades.

The closer the proposed change is to the status quo, the less likely the range of disagreement, but since we are talking here about relatively radical ideas such as open borders, there could be considerable divergence of opinion.

Closely related to the question of how many is the question of who. Many arguments offered by open borders advocates rely on the crucial idea that migrants self-select, i.e., it is not all that easy to migrate to a new land, and therefore migrants are not representative of the populations they hail from, but rather, are selected for positive qualities. As BK has pointed out in the comments (see for instance here and here) you can’t have your cake and eat it too for selectivity: if your estimate says that 25% of the population from region A will move under open borders, you can’t assume that the average migrant who moves will be selected to be in the top 1% of people from region A.

While the precise economics behind double world GDP estimates tends to be complicated, an important point is that all the estimates of huge economic gains also predict that this happens through large numbers of people moving. If, in fact, large numbers of people do not move, then at any rate these specific estimates are not applicable (there may be other mechanisms by which world GDP might increase considerably, such as innovation, but at any rate the specific estimation exercises of the papers would be flawed if very few people moved). For instance, in his blog post about John Kennan’s paper on Open Borders, Nathan Smith writes:

In predicting the volume of migration, Kennan does not assume that humans are strict homini economici who will go wherever they can earn the most. He writes:

One might initially expect that in a world with open borders, everyone would move to the most productive location. But this ignores the strong attachment to home locations that is evident in the data.

He takes this into account by making the migration decision probabilistic, such that the proportion of people who stay in a country is the same as the proportion of the rich-country wage that is paid in that country. For example, if there are open borders between the US and Puerto Rico, and Puerto Rican wages are 2/3 of those in the US, then 2/3 of Puerto Rican adults would stay in Puerto Rico. This roughly fits the data in that particular case, but there is no theoretical motivation for that particular functional form. Relative to a homo economicus model in which everyone who could earn more elsewhere migrated, this assumption causes Kennan to understate the economic benefits of open borders. On the other hand, it also makes Kennan’s version of open borders less scary than it would be if all who stood to gain economically from migration migrated.

This still posits a large number of people who’d move under open borders. Nathan writes later (emphasis mine):

Now, two big things we would like to know about open borders are (a) how many people would move, and (b) how much would world GDP actually increase. If I’m not mistaken, Kennan could easily derive estimates of these things from his model. But he doesn’t. He doesn’t tell us how world GDP would rise under open borders, in the short or the long run. He doesn’t tell us how many people would move, or where they would come from. I think Kennan’s model implies a short-run increase in world GDP of about 65%, and I’m pretty sure in the long run world GDP would double. Since the increase in the effective labor supply comes from growth in the populations of rich countries where labor productivity is high, I think Kennan’s model implies that rich countries’ populations would more than double due to immigration under open borders.

Another related concern is swamping. One of the main concerns of people ranging from hardcore restrictionists to moderate pro-immigrationers and even some who identify as being pro-open borders is that true open borders would lead to very large numbers of people moving over short time periods in a manner that would strain housing, electricity, water supplies, and other infrastructure in the countries receiving the immigrants. The typical response is to point out that (i) borders can be opened somewhat gradually to minimize the possibility of an immediate flood of people (see here for instance), and (ii) in any case, migration flows will tend to be self-regulating and people are likely to plan ahead at least somewhat before making a big move. Evaluating the legitimacy of swamping as a concern is part of the reason why it’s important to get a handle on how many might move under migration regimes that move the needle considerably towards open borders.

Finally, in addition to the direct relevance of understanding migration counts and selectivity, making correct predictions, or at any rate, refraining from making laughably wrong predictions, can help build one’s credibility as an advocate or analyst of migration regimes in the eyes of others approaching the matter from the outside view.

John Kennan’s “Open Borders”

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This post is going to attempt to do something difficult, namely: bring a contribution to technical economic theory within reach of lay readers. The typical lay reader, or for that matter even an atypically intelligent reader who is not a specialist in economics, could understand little of Kennan’s paper, or for that matter most academic economics papers. I don’t totally understand the paper either, but I think I mostly understand it. I’m pretty sure I understand the main thrust. The work in question is “Open Borders” by John Kennan. If one had to pick one thing to stick in a newspaper headline, it would be Kennan’s prediction that

For the 40 countries in Figure 6 this gives an estimate of $10,798, per worker (including nonmigrants), per year (in 2012 dollars, adjusted for purchasing power parity). This is a very large number: the average income per worker in these countries is $8,633, so the gain in (net) income is 125%. For all of the countries in the Penn World Table that are not at the productivity frontier (as defined above), using GDP data to estimate relative wages, the estimated gain is $10,135, relative to an average income of $9,079, so the gain is 112%. These are of course just rough estimates, relying on a number of strong simplifying assumptions. But unless these assumptions are extremely far off the mark, the results indicate that the gains from open borders would be enormous.

In other words, open borders could double the income of the world’s most disadvantaged people. Far from causing a “brain drain” effect, harming poor countries by poaching productive people, even nonmigrants would benefit from open borders. Furthermore:

These gains are associated with a relatively small reduction in the real wage in developed countries, and even this effect disappears as the capital-labor ratio adjusts over time; indeed if immigration restrictions are relaxed gradually, allowing time for investment in physical capital to keep pace, there is no implied reduction in real wages.

How does Kennan arrive at this conclusion? Via a theoretical model, calibrated to fit certain real world data. The approach is oversimplified and crude, yet at the same time, in some ways, painstakingly subtle… but that’s economic theory for you. The logic must be impeccable, but economists’ tolerance for departures from realism can be opaque at first, then, once understood, rather shocking. But one has to do it. A question like “what would happen if the world opened its borders?” involves such a large departure from current reality that common sense and experience fail us. Theory can, so to speak, see in the dark. It allows us to keep thinking clearly, at least, about very remote situations. But down to business.

After a short intro, Kennan’s first really substantive paragraph is:

Before proceeding to analyze a world economy with open borders, the first question that must be answered is whether restrictions on factor mobility have any real effects. If product prices are the same across countries (because there is free trade and transportation is not costly, for example), and if there are two goods that are produced in two different countries, and if the production technologies (for these two goods) are the same across the two countries, then the factor price equalization theorem applies. That is, real wages and other factor prices are equalized across countries even though factors are immobile, because differences in factor prices are implicitly arbitraged through the product market. The theoretical argument is beautiful, but of course the facts are otherwise. For example, wages in the U.S. are about 2.5 times the Mexican wage, for comparable workers.

This will require some unpacking, especially “factor price equalization” and “differences in factor prices are implicitly arbitraged through the product market.” An important result in international economics is that in the “long run,” given certain fairly standard (albeit apparently unrealistic) assumptions, immigration will not reduce wages in the host country, because the mix of industries in the host country will shift to accommodate the new supply of workers to such an extent that wages will be exactly the same. (See the closely related Rybczynski theorem.) Thus, to use the example from the Feenstra and Taylor textbook that I teach this stuff out of, suppose there are two industries, computers and shoes. Computers are a capital-intensive industry, shoes a labor-intensive industry. If a lot of immigrants enter a country called, say, Home, then Home will start producing more shoes and fewer computers.

Fewer computers? Yes, fewer. Even though there are more workers? Not just proportionally fewer? No, fewer in absolute terms. Think of it this way. There’s the same amount of capital in Home as there was before. But there are now more workers. It’s not surprising that the shoe industry will take the lead in absorbing these workers, since its technology is the more labor-intensive of the two. But as it does so, it will lower the marginal product of labor and raise the marginal product of capital in the shoe industry. Or to try to express it without the jargon, the shoe industry will have trouble finding useful things for so many new workers to do without new machines, structures, and other capital goods for them to work with. Even if the shoe industry can’t increase its capital at all, it could find something for all the new workers to do. It will be able to make more shoes. But not that many more shoes. The greater supply of workers increases the shoe industry’s demand for capital. In fact, it implies that the shoe industry wants capital more, at the margin, than the computer industry does. As capital moves from the computer industry to the shoe industry, workers move too, since the scarcity of machines makes them less productive in computers. Importantly, the relative price of computers and shoes stays the same. This is because prices are pinned down by international trade: any deviation in the relative price would cause arbitrage. Wages don’t fall– again, this is in the long run– because relative prices don’t fall, and wages depend on relative prices. The growth of the shoe industry and the shrinkage of the computer industry raise the economy’s demand for labor relative to capital, exactly canceling out the tendency for a greater supply of labor to reduce its wage. This implies not only that wages shouldn’t be reduced by immigration, but also that wages should be the same in every country. Continue reading John Kennan’s “Open Borders” →

New paper on open borders by John Kennan

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John Kennan has come out with a NBER paper titled Open Borders (ungated PDF). The paper is heavy on mathematical economics, and adds to a growing literature that indicates that relaxing immigration restrictions would have massive utilitarian benefits while the negative effect on native wages would be small. I haven’t had time to go through the paper in detail, but here’s the abstract:

There is a large body of evidence indicating that cross-country differences in income levels are associated with differences in productivity. If workers are much more productive in one country than in another, restrictions on immigration lead to large efficiency losses. The paper quantifies these losses, using a model in which efficiency differences are labor-augmenting, and free trade in product markets leads to factor price equalization, so that wages are equal across countries when measured in efficiency units of labor. The estimated gains from removing immigration restrictions are huge. Using a simple static model of migration costs, the estimated net gains from open borders are about the same as the gains from a growth miracle that more than doubles the income level in less-developed countries.

While you’re reading the literature on open borders, check out the pro-open borders reading list on this site, which includes a mix of web articles, research papers, and books. If there’s one research paper on open borders you should read, it is Michael Clemens’ “trillion dollar bills on the sidewalk” paper (ungated PDF).

H/T: Arnold Kling