For decades, the retirement of the baby boom generation has been a looming economic threat. Now, it’s no longer looming – it’s here. The recession may have delayed the inevitable for a time. The financial crisis wiped away billions in retirement savings, forcing many Americans to work longer than planned.Now that the wave has begun, nothing is likely to stop it. The Census Bureau on Tuesday released a pair of reports that show just how dramatic an impact the graying of the population will have in coming decades.