Unauthorized workers are paying an estimated $13 billion a year in social security taxes and only getting around $1 billion back, according to a senior government statistician.

Stephen Goss, the chief actuary of the Social Security Administration (SSA), told VICE News that an estimated 7 million people are currently working in the US illegally. Of those, he estimates that about 3.1 million are using fake or expired social security numbers, yet also paying automatic payroll taxes. Goss believes that these workers pay an annual net contribution of $12 billion to the Social Security Trust Fund.

The SSA estimates that unauthorized workers have paid a whopping $100 billion into the fund over the past decade. Yet as these people are in the US illegally, it is unlikely that they will be able to benefit from their contributions later in life.

In the latest episode of Immigrant America, VICE News documented how most US dairy farms depend on the labor of unauthorized workers, as they simply can’t find enough Americans and don’t have a way of hiring foreign workers legally

Farmers claim that they’re following the law the best they can under the circumstances. Michael, a farm owner who asked for his last name to be withheld, argued that his unauthorized employees don’t get a free ride. He told VICE News that they pay taxes and are hired in accordance with the government’s I-9 requirement.

Unauthorized workers usually demonstrate their employment eligibility with fake IDs and fake social security numbers. Once hired, these “questionably documented” workers, as Michael calls them, end up on the payroll and have taxes automatically taken out of their checks, like any other employee. That money then goes to the federal treasury to fund programs like Social Security and Medicare.

You can read more about the SSA estimates of the unauthorized population’s contributions to the trust fund here.