I have a hard time believing that Argentina is the only one that misrepresents the numbers or that it's the worse city (for robberies or in general) of all of the Americas.
I'm not a crime denier -we live on guard like everyone else and take precautions in our everyday life to try to stay safe, and frankly I'm more than annoyed at the 'justice' system

- but the little I know from people who lived in Venezuela, Costa Rica, or Colombia gives me the sense that Argentina isn't
that bad. This isn't Juarez Mexico. Just as there's fear and a sense of uselessness of going to police here, I'd venture to stay it's the same in a lot of these other countries. Who is going to care about your stolen lawnmower if the police are busy with drug cartels and gangs? I think experience is more valuable than statistics in these cases when judging the relative safety of a city.
That's not to say Argentina doesn't have a crime problem... I just would take this 'report' and #1 ranking with a grain of salt.