Rise in Aggressive Behavior

I was asked by a training client yesterday why there seems to be so many dogs with aggressive behaviors. My two answers were puppy mills & owners being too busy. It is so expensive to live in the tri-state area of NJ/NY that most homes have both adults working. Add children & there list of sports & activities to the mix and there is little time left over to properly socialize, train and spend quality time with the family dog. It seems that most dogs who come to this area from the south via transports are much more laid back & have less aggressive tendencies & behavior issues. I don't doubt it has something to do with the calmer attitude of those living in the south and even though I don't agree with it, many of these dogs are let to run loose rather than being couped up in crates all day while their owners are at work. If anyone else out there has a hypothesis on why there seems to be more dogs with aggressive behavior issues, please post a comment. I'd love to hear what you think.