As is currently the case with the refugee crisis in Europe, every now and then news appears in the media reminding us of the large numbers of people crowded together at specific locations of our borders, close to them or at neighboring countries, from which they try to enter our territory. People take fright before the growing size of these multitudes, believing that our own economy will not be able to absorb such a large number of individuals and they call for the strengthening of the borders, the building of higher walls and the intensification of controls. The horde of emigrants is considered as the problem and borders as the solution. Stated in this way the problem seems to predate the solution.
However, is this really the case? Let us imagine a town located in a valley crossed by a small river. This river flows naturally from the higher points of a nearby mountain passing through the town to the sea. The town inhabitants benefit from the water carried by the river. Now, let us imagine that a gigantic dam is built in the river at some point (no matter why). Over time the dam is filled. The inhabitants begin to take fright before the possibility of overflowing or breakage and call for the building of a larger dam. However, the river flowed naturally and did not suppose any problem until the construction of the dam, which generated a problem that did not exist previously. In the same way, if borders did not exist there would be a natural flow of people migrating from poor zones to richer zones, as it has always happened through history.
In certain locations, there would be a high supply and a low demand for labor. The resulting low wages would contrast with the higher wages of richer locations, which would provide the incentive for migration. However, circumstances and opportunities would not be the same for all and some people would not be willing to assume the costs of a long journey and an uncertain future. The first ones to undertake the journey would be, perhaps, the more intrepid and desperate or those able to raise the necessary capital. With the increasing flow of people from one location to another, the price difference of labor would gradually decrease. The decrease in the supply of labor in the location of origin would cause an increase in its price. The opposite would happen in the place of destination: the increase in the supply of labor would cause a decrease in its price. This process implies that at some point the monetary gain would not be enough to cover the costs of the journey. However, this would not affect everyone equally. It would be dependent on the specific circumstances of every person and place. Circumstances, either in the places of origin or in the places of destination, are constantly changing and this changing information is transmitted through the market. Thus, people can acquire information about different places which permits them to assess the possibility of migrating to one of them.
Sometimes It is said that this last point is not true, that immigrants have no information and would keep on moving to a certain place despite low wages and a shortage of employment, acting irrationally, until sinking it with their weight. Living conditions in the places of destination may seem poor to the local population but, for the immigrants, they surely seem better than those they move away from. It is a strange coincidence that most of them want to migrate to the United States or Europe if they do not use information for choosing the place of destination.
We can observe all this process in the domestic migratory flows of a country. It never happens that all the population of a country suddenly migrates at once to the same city. People want to improve their living conditions and they will stop migrating to a certain place as soon as it does not help them to achieve such improvement.
Thus, we can see that borders and walls are not the solution to the agglomeration of immigrants but its cause.
Most people do not see domestic immigration as a problem. This raises another question: why, then, is international immigration harmful? Maybe both kinds of immigration are. In that case, borders would be also necessary between districts and towns, which is clearly absurd. Maybe there is a size from which immigration becomes harmful but, since there are countries of all sizes, how do we know what is the correct size? It is difficult to defend the need for borders between two countries when there are countries with no internal borders that are larger than those two countries together.
The natural flow of people from some places to others is not detrimental but beneficial. In this way the labor force shifts to those places where there is a higher demand (nobody would say that the movement of tomatoes from a place where there is an abundance of them to a place where there is a shortage is detrimental). Immigration increases the population. However, more populated locations are usually richer locations. The increase in population usually fosters the specialization of knowledge which, along with capital accumulation, makes possible the lengthening of the structure of production that culminates in the increase in wealth, with a larger quantity and better quality of goods at lower relative prices.