According to an Italian study published in the Journal of Marketing Communications, with beards come credibility, which the authors define as a combination of attractiveness, trustworthiness and expertise. The "Beardedness in Advertising" findings indicate that the public trusts bearded men hawking products more than clean-shaven ones. But the Chronicle of Higher Education also points out that the bearded charm doesn't apply to all products, specifically men's underwear. Unfortunately, that also eliminates yet another career revival option for the mustachioed Brawny Man of yore.
The marketing researchers did point out that well-groomed beards could win male politicians more votes by boosting their "charisma, reliability, and above all their expertise as perceived by voters, with positive effects on voting intention." Just ask Benjamin Harrison, the last American President to wear a full beard - and quite a robust one at that - while in office.
Since you can't access the full study for free online, Matt McInerney's Trustworthiness of Beards scale is a go-to for any man hoping to up his cred by sporting whiskers. And guys, however you choose to manicure your facial landscape, please, just steer clear from the soul patches.