Final answer:
Immigration is the contributing factor to the increase of racial and ethnic diversity in the workforce as people move to the U.S. for job opportunities.
Step-by-step explanation:
The factor that is likely a contributing factor to the increase of racial and ethnic diversity in the workforce is immigration. Immigration contributes to workforce diversity because people move from places with fewer jobs to places with more opportunities, such as the United States. This trend has continued despite economic fluctuations. Additionally, changing demographics, such as the aging of baby boomers, affects the workforce composition, but it is not directly related to the increase in racial and ethnic diversity.