As of summer 2015, 10 states and the District of Columbia now issue driver's licenses or similar documents to immigrants in the country illegally, according to a new report from Pew Charitable Trusts.

California, Colorado, Connecticut, Illinois, Maryland, Nevada, New Mexico, Utah, Vermont, Washington and the District of Columbia all issue driver's licenses or similar certification to illegal immigrants.

Nearly 37 percent of all illegal immigrants in the U.S., or about 4.1 million immigrants, live in a jurisdiction where they can obtain a license.

Furthermore, Hawaii and Delaware recently enacted similar laws but have not yet started issuing licenses, Pew said.

States are allowed to decide whether an illegal immigrant can apply to become a licensed driver, often making their decision after weighing "the impact on public safety, insurance and accident rates," reported the Washington Free Beacon. Because of their undocumented status, states also have to pay closer attention to fraud as well as the use of false identities, addresses or documents to obtain licenses.

Pew said some states developed various methods to process those immigrants who don't have U.S. government-issued identification documents.

"Seven states and the District of Columbia require applicants to translate foreign-issued identity and residency documents into English," the report said. "Four offer special procedures so that those who do not have the required documents can be considered on a case-by-case basis."

The largest unexpected expense was the cost of hiring new personnel to process the immigrants' applications, Pew said.

"The number of potential applicants affects staffing and facility needs, license processing and issuance, and expected costs and revenue," Pew said. "The cost of new personnel was the largest anticipated expense."

The driver's license policy resulted in California, Illinois, Connecticut, Maryland, Colorado, Nevada and the District of Columbia creating an extra 1,039 positions to handle applications.

"California's fiscal summary estimated costs of approximately $140 million to $220 million and application fee revenue of approximately $50 million over three years," Pew said. "That assumed 1.4 million unauthorized immigrants would apply for driver's licenses over a three-year period. The state's 2014-15 budget allocated $67.4 million to issue licenses to unauthorized immigrants and included a mechanism for increasing funding if the number of applicants proved unexpectedly high."

Since California began allowing illegals to obtain driver's licenses in January, some 442,000 undocumented immigrants have applied, 35,000 in July alone, according to the San Diego Union-Tribune.