A new study has found that the number of undocumented immigrants in the United States is more than double what was previously estimated.

Two Yale professors and an instructor at MIT Sloan School of Management conducted the extensive research and found that there are 22.1million illegal immigrants in the country.

The widely estimated number is thought to be around 11.3million, but researchers Edward Kaplan, Jonathan Feinstein and Mohammad Fazel‐Zarandi claim that is way off.

'Our original idea was just to do a sanity check on the existing number,' said Kaplan, a professor of operations research at Yale School of Management.

A new study found that there are over 22million undocumented immigrants - more than double the previously estimated number

Researchers Edward Kaplan (left), Mohammad Fazel‐Zarandi (center) and Jonathan Feinstein (right) conducted the study and released their findings this week

A graph that depicts the estimated number of undocumented immigrants that is widely used and the number the researchers found

'Instead of a number which was smaller, we got a number that was 50 per cent higher. That caused us to scratch our heads.'

Feinstein added: 'There's a number that everybody quotes, but when you actually dig down and say, "What is it based on?" You find it's based on one very specific survey and possibly an approach that has some difficulties. So we went in and just took a very different approach.'

The researchers used operational data such as deportations and visa overstays as well as demographic data like death rates and immigration rates to achieve their number.

Kaplan said the model they used is very simple logic.

'The population today is equal to the initial population plus everyone who came in minus everyone who went out. It's that simple,' he said.

'The analysis we've done can be thought of as estimating the size of a hidden population. People who are undocumented immigrants are not walking around with labels on their foreheads. ... There are very few numbers we can point to and say, "This is carved in stone".'

The researchers also found the greatest growth of undocumented immigrants occurred in the 1990s and early 2000s. Pictured is a border patrol agent apprehending illegal immigrants shortly after they crossed the border from Mexico in March

According to Yale Insights, the researchers also found the greatest growth of undocumented immigrants occurred in the 1990s and early 2000s. They also said the population size has been relatively stable since 2008.

'The trajectory is the same. We see the same patterns happening, but they're just understating the actual number of people who have made it here,' said Fazel‐Zarandi, a senior lecturer at the MIT Sloan School of Management and formerly a postdoctoral associate and lecturer in operations at the Yale School of Management.

'They are capturing part of this population, but not the whole population,' he added.

All three researchers said they did not conduct the study with a political agenda, but know their findings will get 'pulled and tugged in many ways'.

'Our purpose is just to provide better information,' Feinstein said. 'This paper is not oriented towards politics or policy. I want to be very clear: this paper is about coming up with a better estimate of an important number.'

He added: 'We wouldn't want people to walk away from this research thinking that suddenly there's a large influx happening now. It's really something that happened in the past and maybe was not properly counted or documented.'