We’ve all experienced this. You’re at a crowded party, parked (wisely) next to the bar. A new guest comes in, quickly shoves a middling bottle of wine into the cooler amidst the “hi, how are you” chaos, and then makes a beeline for the good stuff.

You watch in disbelief as dude or dudette pours a giant glass of the $25 Riesling you sprung for, smiling at you over the brim—we’re talking bowl-full here—before taking his or her first big gulp of your hard-earned Austrian minerality.

Or maybe it’s not wine. Maybe it’s an ironic six-pack of Miller High Life, shoved unceremoniously into the fridge, never to be seen again, while New Guest takes her keychain church key to your $14 bourbon barrel-aged stout four-pack. What you’re witnessing isn’t simply an egregious party foul. It’s a longstanding sociological phenomenon, and quite possibly, the downfall of polite beverage civilization, known simply as the free rider problem.

“The Free Rider” is actually an economic term referring to those “individuals in a population [who] either consume more than their fare share of a common resource, or pay less than their fair share of the cost of a common resource.” And while said Free Rider would be, and generally is, a far greater drag in more serious socioeconomic and political contexts, we can’t deny he or she exists in the (relatively) muted tragedies of uneven BYOBs.