My mother works as a visiting nurse in Newark (NJ) and is certain that the cause of the social decay in the city is mainly the huge rate of teen pregnancy. Teenagers have children out of wedlock and do not raise them, and the cycle feeds on itself as those kids grow up (or really, just hit puberty) and do the same thing.
I had a long talk with her about it a few months ago, and this is essentially what we thought the causes and primary solutions might be:
Inner city children typically receive little to no attention growing up. As they are constantly ignored, they act out more and more to try to get noticed. Eventually, to resolve the issue, boys/men typically will join gangs or hang out with their friends, and the girls/women will do the same, with one big exception. As soon as a woman becomes pregnant, she received huge attention. From social groups, from church groups trying to prevent an abortion, from doctors/hospitals, formula manufacturers, and just about anyone else you can think of. When the baby is born, she is in a huge position of responsability, and in charge of a person receiving tremendous attention. This lasts 5 months to a year, and gradually tapers off. As the baby stops generating interest for the mother, the mother pays less attention to the baby, the baby receives little to no more attention as it grows, and the cycle continues.
There are lots of other factors in play, of course. The way culture portrays sexuality and gender roles is also a huge contributor, the welfare system, and I'm sure there are lots of others I haven't even considered.
After brainstorming the problem for a few hours, the only direct, impactful action, I could come up with was this:
You have to reward impoverished men and women, financially, for not having children. Very dark and China 'esqe, I know. It will probably never happen. My feeling is that the only way this ever will improve is through a very gradual shifting of inner city demographics and the gradual lifting of this segment of the population out of poverty. Not a very pretty picture.