You're right on the difference in birth rate, but I don't agree with violent deaths being the main cause over all.
Sure, for young men they do indeed count for more deaths than young women, but at an older age women definately live longer than men.
Here's one statistic from USA for you:
statistic said:
In 1999, there were 20.2 million older women and 14.3 million older men, or a sex ratio of 141 women for every 100 men. The sex ratio increased with age, ranging from 118 for the 65-69 group to a high of 237 for persons 85 and over.