Developers have shunned building affordable housing, in part, because the receipt of government funds requires them to utilize expensive union labor.
This put Bill DeBlasio in a bind. He could either build not as much housing, or simply not enforce the requirements. The latter would have really annoyed unions.
Instead, a compromise has been reached: Unions have agreed to a 40% pay cut in exchange for being relevant.
http://www.cityandstateny.com/2/83/labor/rebuilding-the-trades.html#.U__efxZtdz-The hope of unions is that someday the public will again care about their plight when they errect the rat.