Online job boards are the most popular recruiting tools for hiring managers at small and midsize businesses, according to a study released this week.

More than half of the 408 hiring managers polled by the Inavero Institute for Service Research used online job boards for recruiting during the past year. Their recruiting budgets were also shifting toward online job boards and other less traditional media, the Oregon-based service research firm reported.

Online recruiting is also the cheapest hiring tool available, costing an average of $291 per candidate hired. Traditional media efforts like newspapers, television, and radio job listings cost 500 percent more per average hire, according to the study.

Less than half of the respondents said they used newspapers as recruiting tools, and local papers were primarily used to attract hourly, blue-collar workers, with a salary range of $30,000 or less. Professionals who require higher salaries were more often found through referrals and online job boards.

Despite increased reliance on less traditional recruiting methods, referrals are still the most trusted recruiting tool and produce the highest quality job candidates, the study found. Nearly 46 percent of white-collar jobs are filled this way.

The results of this survey directly contrast a May study by the Conference Board, in which the number of online job listings had dropped compared to the same time period in 2007. The survey did not compare Web listings to recruiting efforts in traditional media.