Investing in a second passport? Look no further than a tiny Caribbean haven for the most bang for your buck, according to a new study.

Second passports have become de rigueur among the world's wealthy, particularly for those from countries such as China or Russia who may otherwise face travel restrictions due to their citizenship.

The industry has burgeoned into a $2 billion moneymaker. For the super-rich, the schemes offer an avenue to bring part or all of their assets outside their home country and usually a wealth-friendly tax system, all for a relatively modest flat fee or real estate investment.

But for-purchase schemes differ. Which are the best?

Caribbean Tops Ranks

Dominica, a rugged island just south of Guadeloupe, topped an annual ranking compiled by trade publication «Professional Wealth Management» together with CS Global Partners, a London-based law firm which facilitates such schemes. 

The study evaluated only passports for sale, unlike a similar annual ranking which looks at overall attractiveness of citizenship. The Caribbean island topped the league table for its affordability, ease of processing, mandatory travel requirements and strong due diligence parameters, the study's authors said.

For countries offering citizenship by investment (CBI), the schemes offer an easy and reliable way to replenish state coffers – after all, there will always be super-wealthy seeking to diversify.

Ill-Gotten Funds

It can also be a quick way to draw in ill-gotten funds: Jho Low, who is accused by U.S. prosecutors of being the mastermind behind the illicit money trails out of state fund 1MDB and into private coffers, was recently reported to possess citizenship from St. Kitts and Nevis, a neighbor to Grenada and Dominica.

St. Kitts, which came in second place in the ranking in part for «its reputation of integrity and trust», recently revoked an American lawyer's passport after he was accused of pilfering funds to buy it.

Grenada, which reopened a passport scheme four years ago, finished third. Antigua and Barbuda and Saint Lucia rounded out the all-Caribbean top five.

The least desirable of the 12 passport by investment schemes polled? Those of Austria and Cambodia.