From the Document: "Congress has demonstrated ongoing interest in the global migration crisis, particularly with recent flows of migrants and refugees to the United States from Central America and Mexico. In 2019 an estimated 272 million international migrants formed roughly 3.5% of the world's population. Although not formally defined under international law, many experts generally agree that an 'international migrant' is someone who changes his or her country of usual residence, temporarily or permanently, and for a variety of reasons. The decision to move is usually made out of a choice related to livelihood, improved economic circumstances, or family ties. However, as discussed below, certain factors may force individuals to leave involuntarily."
CRS In Focus, IF11003
Congressional Research Service: https://crsreports.congress.gov/