It was the most consequential leak in the history of the offshore world, providing journalists and the public an unparalleled view into a notoriously shadowy industry that shuttles secret wealth around the globe.

In 2007, an engineer extracted detailed records on the hidden wealth of more than 30,000 clients of HSBC Private Bank, the Swiss subsidiary of the British multinational banking giant, and secreted them to the French government. The data, which eventually became known as the “Swiss leaks,” ended up in the hands of other authorities and journalists.

Now, that data, along with the Panama Papers – the records of a Panamanian law firm dealing heavily in offshore finance that were leaked to journalists last year – is providing academic researchers with a valuable look inside the opaque world of tax evasion and offshore holdings.

In a newly released paper, researchers in Scandinavia and the United States use the Swiss and Panamanian leaks to show that global tax evasion is likely much more prevalent than previously thought. Their estimates indicate that the top 0.01 percent of the wealth distribution own about half of all offshore assets and may be hiding roughly a quarter of their wealth offshore.

“Most of the tax evasion happens at the very, very top of the wealth distribution,” said Gabriel Zucman, one of the researchers.

Zucman has previously estimated that the equivalent of about 10 percent of global gross domestic product is hidden in tax havens. These countries, which often have laws that ensure the secrecy of offshore accounts, include Singapore, Hong Kong, Luxembourg, the Cayman Islands, the Bahamas, and Switzerland – which alone manages an estimated 40 percent of the world’s offshore wealth.

The researchers matched up individuals present in the leaks and random tax audits with wealth records from Scandinavia. Those countries offer particularly detailed records on the wealth of their populations, allowing researchers to figure out what the distribution of offshore accounts might look like among different economic classes.

Their estimates show that the wealthiest people are getting away with paying far less than their fair share.

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