“Social Security reform” is one of those soundbites you might hear every election cycle without anything ever changing. Politicians have been sounding the alarm for decades, saying that the program — which helps retirees, people with disabilities, and their families stay afloat — is quickly running out of money. So what’s actually at stake? Social Security is a pay-as-you go system, so taxes collected from today’s workers are spent on current beneficiaries. But because the workforce hasn’t...