Happy Birthday? Age Labels, Search Criteria, and Matching from Dating to Marriage

Age is a match trait and a prominent label on search platforms. Using confidential records from a large Japanese marriage platform, I study how a birthday age update affects consideration, applications, relationship progression, and engagement. Only displayed age updates at birthdays. Receivers enter some acceptable-age ranges as they exit others, leaving only modest overall eligibility changes. Application counts often increase. Applications shift from younger to older suitors. Proposal counts fall at nine of ten female receiver ages \(31\text{--}40\), with losses concentrated at entry into early dating. In stage-specific accounting for receivers in their thirties, the no-birthday proposal count is \(12.9\) percent above the benchmark for female receivers and \(6.7\) percent below it for male receivers; the younger-man share in the female-receiver channel is \(4.8\) percentage points higher. Age labels and filters are not neutral windows onto preferences: they govern who marries whom and how many marriages form.