American taxpayers cannot afford the cost of amnesty.

The cost of illegal immigration and amnesty could amount to $6.3 trillion, which would fall on American taxpayers over the long term, according to a Heritage Foundation analysis. As Heritage showed, the majority of illegal immigrants receiving amnesty would receive far more in taxpayer-funded benefits than they would pay in taxes. Even critics of the Heritage study admit amnesty will cost trillions of dollars. Whether it is $4 trillion, $6 trillion or more, the additional costs to the U.S. taxpayer are still too high.

Here are a few factors that could drive the cost even higher.

1) The number of illegal immigrants may be higher.

Heritage’s analysis is based on the Department of Homeland Security’s estimate that there are 11.5 million illegal immigrants currently in the United States. “The DHS estimates that there are some 10.4 million unlawful immigrants recorded in Census surveys and 1.1 million more who are not reported by the Census,” explains Heritage expert Robert Rector. The first number is based on evidence, but the second is a guess, meaning there may be far more. If the number of illegal immigrants is actually 20 percent greater than the 11.5 million assumed in the Heritage analysis, the long-term fiscal cost of amnesty would increase proportionately, adding perhaps $1.2 trillion to the lifetime fiscal deficit.

2) Medical and welfare inflation in future years is likely to increase future costs.

The Heritage analysis is based on the very conservative assumption “that means-tested welfare and medical benefits per household will grow no faster than general inflation for the next 50 years.” However, Rector explains, “the historical record suggests that this is highly unlikely. For nearly every year for the past half-century, welfare spending per capita has increased much faster than inflation.” It is a similar story for medical care. “The main analysis in this paper assumes that the cost of medical services per beneficiary will grow no faster than inflation for the next 50 years,” says Rector. “This is likely an underestimate and probably results in an understatement of future spending.”

3) Because the analysis measured costs mainly by household, it likely excluded about 20 percent of illegal immigrants.

The Heritage analysis estimated the pre-retirement costs for households headed by illegal immigrants (excluding legal adult residents who might live in those households). But Rector explains that “about 20 percent of unlawful immigrants do not reside in those households. Any pre-retirement fiscal costs associated with that 20 percent are therefore omitted from the analysis; this is likely to lead to an underestimate of total costs.”

4) Amnesty may act as a “magnet” for future illegal immigrants.

The United States passed amnesty in 1986 under the promise that no future amnesty would be granted. “Despite this promise, the 1986 amnesty was probably a factor in encouraging the subsequent surge in unlawful immigration, since it signaled that the U.S. might take a lenient stance toward unlawful immigrants in the future. If the U.S now enacts a second amnesty, it will have established a very strong precedent for serial amnesties,” says Rector.

Obviously, $6.3 trillion is a major cost to American taxpayers, particularly considering the United States’ current debt of $17 trillion. American taxpayers should be fully aware of the financial burden amnesty would impose.

As Heritage Foundation President Jim DeMint also noted: “Any immigration reform should improve the lives, the incomes, and the opportunities” of those lawfully in the United States. Burdening taxpayers is not fair to everyone who lives in the U.S. legally.