Everywhere in the world women live longer than men - but this was not always the case. The available data from rich countries shows that women didn't live longer than men in the 19th century. What's the reason women live longer than men? And how the advantage has grown in the past? We only have partial evidence and the evidence is not sufficient to draw a definitive conclusion. We know that biological, behavioral and environmental factors play a role in the fact that women have longer life spans than men, However, we're not sure what the contribution of each one of these factors is.