The weirdest results were in Queens.
If the Census is to believed, the 7-train corridor in Queens (the busiest train line, by far, in NYC, and the heaviest immigrant corridor) has a massive amount of apartments sitting vacant.
I'm no demographer, but I find it hard to believe that Flushing and Jackson Heights are filled with empty apartments everywhere.
The only possibility would be gentrification, where immigrant families are being replaced by small household sizes, but honestly, when you visit Flushing, do you feel that hipsters are rapidly replacing Asian families?
I obviously have no evidence, but I'm guessing the Census has a problem with immigrant response rates. Does Main Street in Flushing strike you as massively overcrowded, or half-empty?