Europe has what you may call a man problem.
Since the beginning of the 20th century, researchers have found a growing increase in the ratio of men versus women in many of these countries. A recent report published at Phys.org says that Sweden specifically has seen a historic gender shift. For the first time since record keeping began in 1749, the country’s population contains more men than women.
Men tend to become more promiscuous when sex ratios are skewed towards more women, but more violent when sex ratios are skewed towards more men.
From what I can tell from the article, most of the increase in male population is due to migration – probably due to conflicts in the Middle East. Incoming migrants may experience social isolation in their new home and PTSD from the conflicts they are fleeing, which has the potential to exacerbate violence. I hope Sweden is able to give adequate support to its new residents.