Did you know that when your employees leave the office, nearly a third (32 percent) have another job? That's according to a survey from CareerBuilder. Some may freelance with their professional skills, others probably work new-age gigs with companies like Uber, and a few might rake in some extra cash by serving drinks at the local bar. Either way, it's interesting to know which groups of employees are most likely to pursue these opportunities.

Several factors influence the probability of an employee having a secondary job, including age, gender, race, earnings, and job function.

Workers under the age of 35 (41 percent) are more likely to have a side hustle than those older than 35 (27 percent). Women (35 percent) are more likely to do so than men (28 percent), and black and Hispanic workers (46 percent and 40 percent, respectively) are more likely than white and Asian workers (29 percent and 26 percent, respectively). Looking at earnings, 35 percent of people making less than $50,000 have a side job, compared with 25 percent of those earning more than $75,000 and 19 percent with a salary of more than $100,000. In terms of job function, side hustles are most popular among those working in leisure and hospitality (42 percent), followed by those in transportation (36 percent) and healthcare (34 percent).

A final factor that can increase the likelihood of someone having a second job is location. In certain large cities, such as Dallas (40 percent), Boston (39 percent), Houston (39 percent), and New York (38 percent), people are much more likely to earn a supplemental income.