More than half the votes in the recent US presidential election were cast in electronic machines that could have been tampered with or stolen, according to new research.
The research, which is published in the journal Nature, found that just 1.8% of all votes cast in the election were recorded by optical scanners, compared with more than 40% in 2012.
The report, published on Monday by the Carnegie Endowment for International Peace (CEP), a US think tank, is the latest in a series of research that shows how the growing use of smartcards, microchip and other technologies has made it easier to hack votes.
In November, a study by a team of researchers found that nearly 80% of voters had voted in the US by using a smartphone app.
In May, a survey of 1,100 US voters found that 80% had voted using a mobile app, and in September a survey by researchers at the University of Wisconsin found that almost half of all voters had done so using a digital vote scanner.
The latest study is the first to look at the accuracy of optical scanners at this level of detail.
“The question we asked is, can we make it even more accurate to be able to vote using a machine with an electronic punch card, but also with a paper punch card,” said researcher John Dickson, who led the study.
In addition to being more accurate, the scanners were cheaper to use.
Using a microchip or a chip reader, which use a computer to read a barcode, requires expensive equipment.
And the scanner used in the new study is still in use by some states, which require them to be replaced every five years.
“There’s no reason for the voting machine industry to have an electronic chip in their voting machines,” said Dickson.
Electronic voting systems, which are being rolled out in a number of countries, have made it much more difficult for hackers to take control of machines that have been hacked in recent years.
The researchers also looked at how the machines themselves work and found that while they do use a digital memory card, there was no way to hack the card, although the card is not designed to be tampered.
“I think this is the most important finding from this study,” said Paul Johnson, a voting technology expert at the American Civil Liberties Union in Washington DC.
“If we want to make sure we can have confidence in the integrity of the vote, we need to make it more accurate.”
The researchers found a similar pattern in another recent study that looked at the use of optical scan voting machines.
A paper published in December found that only 7.7% of votes cast were recorded, but in that study only a small number of machines were vulnerable to a hack.
Electoral fraud, in which someone votes for someone else by using an automated system, is extremely rare.
The only known cases of this kind of fraud were recorded in the 2004 presidential election, when a Democratic National Committee voter impersonator was convicted and sentenced to five years in prison.