There are still a lot of people moving into NJ from NY/NYC. NY/NYC is not the best place to live these days, but people still want access to those NYC/NY jobs that pay big $$$$
So they move to North/Central NJ where they can live in a safe(r) and cheap(er) area compared to where they came from in NY/NYC, while still being a reasonable distance from NYC/NY where a commute isn't that bad.
That being said tons of people further South in NJ are moving out. Not to mention, all these housing developments being built are meant to house only a couple of people, much less families. Far cry from the giant houses that were being built for big(ger) families in NJ some 20-30 years ago...