Bad news is more sudden than good news, which is usually gradual. Therefore bad news is more newsworthy.
People vastly overestimate the frequency of crime, because crime disproportionately dominates the news. But random violence makes the news because it is rare, whereas routine kindness doesn’t make the news because it is so common.http://www.rationaloptimist.com/blog/the-persistent-appeal-of-pessimism/
People have a negativity bias. The good news is that the world is doing better than you think.