Countries across Europe have been operating under the assumption that by sending more money overseas, it will stop people migrating. The only problem? There’s little evidence to suggest that this strategy works.

When Sebastian Kurz, now the world’s first millennial leader, was Austria’s minister for foreign affairs, he announced a simple plan to reduce migration; dramatically increase his country’s foreign aid budget. In the same year (2016), Britain pledged to spend aid money more efficiently so its creates jobs in poorer countries to “reduce the pressure for mass migration to Europe.” The European Union had the same strategy—invest money, tackle the root causes of migration, which would stop people undertaking the dangerous journey to Europe.

But researchers from the Center for Global Development, a Washington DC-based think tank, analyzed the few existing studies on the relationship between aid and migration and noted in it report that the strategy might be having the opposite effect.

Challenging received wisdom that aid deters migration, the report firstly says that “development aid disbursements do not generally follow ‘root causes’ rhetoric.” That is to say the way aid is distributed in countries with high emigration does not significantly differ from its distribution in other countries.

Secondly, researchers suggest that there’s not enough evidence to show that aid that targets the so-called root cause of migration is effective. This aid has failed to kick-start poor economies, meaningfully increase youth employment, or have a significant effect on violence prevention. “Though occasionally intensive job training has reduced youth unemployment, there is scant evidence that such programs can be scaled up to achieve national impacts,” researchers note in the report.

The study goes on to paint a far more complex relationship between migration and economic development. Families often pay significant amounts of money upfront in hopes that it would lead to income gains from overseas work. In short, sending young male relatives abroad is often seen as an investment for the future. Thus, aid that results in greater economic opportunity at home, may end up making “such an investment more feasible,” researchers note.

Researchers admit the “unmistakable negative relationship” between youth employment and emigration; countries with higher youth employment tend to have fewer people leaving. That said, they argue this is true for poor countries that remain poor, noting high youth employment is “unlikely to reduce migration in robustly growing and diversifying economies.” Therefore, as poor countries economies grow, so does people’s income, education, and aspirations. And while emigration levels tend to slow down and then drop significantly once countries develop past middle-income, “most of today’s low-income countries will not approach that point for several decades at any plausible rate of growth.”

The report calls for a better understanding on why and how people in poor countries use migration to improve their lives. Researchers urge policymakers to look beyond deterrence and focus efforts to shape how migration occurs so it’s mutually beneficial.