Last week, the U.S. Citizenship and Immigration Services (USCIS) put into effect a new policy that significantly impacts the foreign student and exchange visitor population in the United States. According to the Department of Commerce, international students contributed $39.4 billion to the U.S. economy in 2016, which created or supported over 450,000 jobs. This new policy constitutes a striking departure from the agency’s previous 20-year long practice.

The policy affects how the federal government calculates a foreign student’s or exchange visitor’s period of “unlawful presence” in the United States. Under a 1996 amendment to the Immigration and Nationality Act, a prior period of unlawful presence may bar a foreign national from returning to the United States for three or 10 years after leaving.