Here are nine investigations on voter fraud that found virtually nothing

The Trump administration is doubling down on unsubstantiated claims of widespread voter fraud in the 2016 presidential election with a call from the president himself to conduct a “major investigation” into whether it occurred.

Trump’s call for an investigation overlooks that there have been numerous inquiries into voter fraud over the past decade, and none of them have turned up evidence of a widespread problem:

In one of the most comprehensive investigations of fraud, Justin Levitt of Loyola Law School, Los Angeles turned up 31 credible instances of voter impersonation out of more than 1 billion votes cast between 2000 and 2014. Some of those cases may have been because of clerical errors. Levitt’s investigation suggests that while voter impersonation does indeed happen, it happens so rarely that the rate is approximately one instance out of ever 32 million ballots cast. This is similar to the odds of getting “heads” 25 times in a row on a coin toss.

A five-year voter fraud investigation conducted by the George W. Bush administration “turned up virtually no evidence” of organized fraud, in the words of the New York Times. While the investigation did yield 86 criminal convictions as of 2006, many of those appear to have been linked to people misunderstanding eligibility rules or filling out paperwork incorrectly.

In 2014, a two-year investigation into voter fraud by Iowa’s Republican secretary of state yielded 27 criminal charges, a number of which, again, were apparently related to mistakes or misunderstandings of voting rules.

There even have been research and investigations into voter fraud in the 2016 election. They come to similar conclusions:

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