Final answer:
Immigration is a key factor contributing to the increase of racial and ethnic diversity in the U.S. workforce, as it brings people from diverse backgrounds into the labor market.
Step-by-step explanation:
A contributing factor to the increase of racial and ethnic diversity in the workforce is immigration. Immigration leads to a more diverse set of individuals entering the labor market, enhancing the racial and ethnic composition of the workforce. The United States has been a destination for immigrants seeking employment opportunities, and this, in turn, has been a significant factor in shifting the demographics of the workforce. Additionally, changing demographics, such as more women entering the workforce since the 1970s and 1980s and moving up within organizations, also contribute to a more diverse workforce. The U.S. Census Bureau projects that the proportion of U.S. citizens who are of Hispanic background will rise substantially, largely influenced by immigration patterns.