How did american companies contribute to the influx of puerto rican migrants by the hundreds of thousands beginning in the 1950s?

U. S. factory owners and employment agencies had begun recruiting heavily on Puerto Rico.

After 1945, economic changes transformed Puerto Rico's economy from a monocultural plantation economy into a platform for export-production in factories through what was called Operation Bootstrap. By the 1950s a growing unemployment problem left thousands of Puerto Ricans in need of a fresh start on American companies.