A Stanford study published in Pediatrics found that fewer than half of surveyed U.S. parents know the federal tobacco purchasing age is 21, despite 82% correctly identifying the alcohol age limit as 21. This knowledge gap matters because parents who don't know the law are less likely to enforce it with teens or reinforce it in household conversations. The finding was published April 14, 2026, based on surveys of over 2,000 parents and caregivers—a rigorous sample that makes the gap in awareness significant for public health messaging.