Much less than 13%. Subtract nearly everyone younger than 10, older than 35 and a goodly fraction of the females from that 13%.
LBJ did us no favors by creating a permanent welfare class and using rules that excluded households from any aid where there was a man in the house to destroy two parent families.
But he did get his 50 years of "those n____rs voting Democrat"!
I believe LBJ said “two hundred years”. So one hundred fifty to go.