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NSA / Reuters The National Security Agency headquarters building in Fort Meade, Md.

Ever since Edward Snowden’s leaks began revealing the extent of the National Security Agency’s mass surveillance—or “bulk collection”—programs last June, officials have defended the programs with one number: 50.

“We know of at least 50 threats that have been averted because of this information not just in the United States, but, in some cases, threats here in Germany. So lives have been saved,” President Obama said on a visit to Berlin. NSA Director Gen. Keith Alexander made the same claim testifying before Congress.

But a new study out Monday from The New America Foundation says that claim is simply false, calling it “overblown, and even misleading.”

“Surveillance of American phone metadata has had no discernible impact on preventing acts of terrorism and only the most marginal of impacts on preventing terrorist-related activity, such as fundraising for a terrorist group,” says the nonpartisan think tank’s report, titled “Do NSA’s Bulk Surveillance Programs Stop Terrorists?”

In an analysis of 225 al-Qaeda-linked individuals charged with terrorism in the U.S. since 9/11, the report found NSA mass surveillance of Americans telephone records—authorized under Section 215 of the USA PATRIOT Act—“played an identifiable role in initiating, at most, 1.8 percent” of investigations.

The report acknowledges that in 28 percent of cases it reviewed, researchers couldn’t determine what methods initiated the investigation. But in many of those cases an informant played a role in the investigation, says the report.

ACLU Legislative Counsel Michelle Richardson told TIME the report “confirms that the numbers and examples the government has floated in support of its domestic spying programs are grossly inflated. More broadly though, it underlines how far the government has actually gotten away from the original lessons of 9/11. Instead of working on connecting the dots collected from traditional investigations, it has become obsessed with collecting ever more data whether it is useful or not.”