True, you didn’t get paid to streamline the database at the local Red Cross office, or organize that huge fundraising auction for Oxfam, or put your accounting skills to work at your church. So it doesn’t really count — right?

Not so fast. According to a new survey from LinkedIn (LNKD), 89% of U.S. businesspeople have significant volunteer experience. Yet only 45% include it in their resumes.

The same report tells why leaving it out is a mistake: 41% of hiring managers say they consider free labor for a good cause to be “equally valuable” as other experience, and one in five has hired someone for a paying job because of his or her volunteer work.

“Professionals often have the misconception that volunteer work doesn’t qualify as ‘real’ work experience,” observes Nicole Williams, whose title at LinkedIn is connection director. “But in the current hypercompetitive job market, when hiring managers or potential business partners are comparing candidates, volunteer experience can be the deciding factor that makes you stand out.”

Williams adds that volunteer work is a great way to rub elbows with “driven, conscientious professionals” who often make great references in a job hunt. “The most successful people dedicate some of their efforts to a cause that extends beyond themselves, and hiring managers are well aware of this,” she says.

For all of those reasons, LinkedIn just introduced a feature that makes it easy for the site’s 120 million members to include a “Volunteer Experience & Causes” section in their LinkedIn profiles. Adding the information to resumes as well would be a smart move.