It's a vicious cycle.
People leave, and that adds to the perception that it's unsafe.
But it isn't just crime. Dr. Elijah Anderson, the Charles and William Day Professor of Sociology, is African American, and has written extensively about issues of race and class and poverty in urban areas like West Philadelphia. But then things started happening. Six years ago, he woke up to find a man trying to break in through his window. A friend was jumped by a group of young toughs, who broke his arm.