The disappearance of these dependents is believed to have involved either children who never existed or tax deductions improperly claimed by non-custodial parents.[10] In 1988, the threshold was lowered to two years old, and in 1990, the threshold was lowered yet again to one year old.[11] Today, an SSN is required regardless of the child's age to receive an exemption.[citation needed] Since then, parents have often applied for Social Security numbers for their children soon after birth; today, it can be done on the application for a birth certificate.[12]