At the median, yes, according to Daniel Kay Hertz:
I recently ran across a post from data-crunching blog extraordinaire Xenocrypt, which noted that from 1999 to 2011, median household income in Brooklyn fell from $42,852 to $42,752…
Furthermore in large parts of Brooklyn real estate prices are falling. You can read more here, with interesting pictures.
The pointer is from Hugo Lindgren.