A lot obviously depends on a person's gender, size, age, etc. Not only your actual capacity to defend yourself, but rather your perceived capacity. For example a petite 19yo female is obviously far more likely to be hassled or attacked than a well-built man in his 30s. This unfortunately holds true, wherever you go. There are many places in the world where I would feel perfectly comfortable, but would advice solo females to avoid like the plague.
Having said that, there are exceptions. I am built like the proverbial brick "outhouse" and that didn't stop a drug-crazed youth pulling a knife on me (in England, btw).