The baby-boomer* generation is much bigger than other generation. Their retirement is not met with the same amount of young worker coming into the job market. Businesses need to produce just as much if not more as before. So basically we need to import the kids we did not have 20 to 30 years ago to maintain the same amount of workers. The same thing is happening in many developed countries.
* Germany's baby-boomers are younger than the one in the USA or Canada