Over the weekend, hundreds of migrants — 800, according to the UN High Commissioner for Refugees, including many children — died when their ship capsized off the coast of Libya. EU leaders have already responded with a 10-point plan to deal with the Mediterranean migration crisis, focusing on increasing sea patrols and dismantling smuggling operations. Italy's former Mare Nostrum operation, a search-and-rescue mission that saved more than 100,000 migrants before being canceled last year, is being held up as a model of how to proceed. "The short-term solution is fairly obvious," Joshua Keating writes at Slate. "The EU as a whole needs a more ambitious plan to rescue migrants."

That's definitely true. But even the best search-and-rescue operation will only manage the problem. It won't go away until life in the EU is no longer dramatically better than life in the migrants' home countries. And while many migrants are fleeing violence and political instability in Libya, Syria, Iraq, and elsewhere, many others are merely fleeing poverty. One survivor of this weekend's ship sinking was reportedly from Bangladesh.

The migrants are making a rational choice. If they make it over to Europe, and are allowed to stay, they will earn not just a little more but much, much more than they would have at home. It's pretty firmly established that workers in developed countries make much more than workers in developing countries doing identical labor. The Center for Global Development's Michael Clemens, Claudio Montenegro, and Lant Pritchett estimate that if the average Yemeni or Nigerian moved to the US and did the same work, he'd make about 15 times as much:

An average Bangladeshi, like the survivor of the Libya ship disaster, would make over four times as much in the US. And while Italy isn't as rich as America, it's not far off. The gains to migrants should be enormous. The gains are so large, in fact, that economic models trying to estimate the impact of completely open borders worldwide suggest the policy would increase world GDP by between 50 and 150 percent, much of which would redound to the world's poorest people, both through their own migration and through remittances sent back to their families.

The rich world spends billions of dollars every year on armed guards and planes and drones to make sure the global poor stay poor

So why doesn't Europe solve this problem by just letting people stay? The case that immigration hurts rich countries like those in the EU economically is so weak that even opponents tend not to make it. The case that it hurts low-skilled workers is heavily disputed and, in any case, addressable through transfer programs within rich countries. The economic case against immigration only makes sense if you're willing to put negative weight on the well-being of foreigners. And evidence that migration to Europe increases crime is sparse, with some studies even finding that areas with more migrants experience less crime.

For such a poorly supported policy, we sure put a lot of effort into maintaining it. The rich world spends billions of dollars every year on armed guards and planes and drones to make sure the global poor stay poor. It wasn't always this way: US and European borders were more or less open until the outbreak of World War I. And it doesn't have to be this way in the future. We can, if we want to, "fast-forward to the world of the future where everyone can enjoy a First-World standard of living," as Bryan Caplan puts it.

The EU won't fast-forward anytime soon. Nationalism is on the rise in the EU at the moment, and is elevating racist anti-immigrant parties like the UK Independence Party or the Front National in France. That means we can expect their response to the migrant crisis to focus more on deterring migrants than on helping them. The UK government even refuses to fund search-and-rescue missions, arguing that they cause "an unintended ‘pull factor’, encouraging more migrants to attempt the dangerous sea crossing and thereby leading to more tragic and unnecessary deaths."

That's not just a morally barbaric position. It's a self-defeating one that will leave Europe poorer and ensure dangerous sea crossings continue for years to come.