How wealthy people are buying passports from other countries.

As migration and inequality continue to get significant attention from the U.S. presidential candidates, it is worth noting a rising phenomenon at the intersection of these two topics: economic citizenship. A growing number of countries offer individuals passports in return for investment, and the wealthy have been taking advantage in increasing numbers. In 2014, the global rich spent an estimated $2 billion acquiring nationalities.

The Caribbean is the global capital of “citizenship-by-investment” programs. A passport from Dominica can be had in return for a $100,000 investment. A $400,000 real estate investment or a $250,000 donation to a development fund will get you citizenship in St. Kitts and Nevis. Similar sums are required for a passport from Antigua and Barbuda, plus five days of residency over the first five years of citizenship. In 2015, Caribbean nations effectively sold an estimated 2,000 passports through citizenship-by-investment programs, up 100% over the past five years.

But it’s not just Caribbean nations hawking passports. Cyprus, for instance, offers citizenship in return for a minimum €2.5 million real estate investment. Further, not all countries sell citizenship outright. Some, including the United States and the United Kingdom, offer residency—and a path to citizenship—to wealthy investors. In the U.S., for example, aspiring citizens that invest $500,000 and create 10 jobs can apply for an EB-5 visa. The UK requires an investment of at least £2 million. Both countries expect investors to spend roughly half the year in residence for several years before applying for citizenship. And almost all economic citizenship programs have fees that are paid directly to governments in addition to the required investment.