Isn't this simply because when these older blacks were younger, they had to face a great deal of racism and poverty in their lifetime, which tends to lead to alcoholism and drug addiction? They had much fewer opportunites, compared to the younger generations. I'm sure there must be a correlation... I would like to believe that if there are less homeless people in general, it is due to societal improvements as a whole (eliminating racism, improving educational opportunities, better treatment and outreach programs, etc).