Cross-Gender Social Ties Around the World

friendships between people of different genders

It means the ratio of friends who are of the opposite gender.

So areas which are more blue mean men have more women friends than they do men, and or women have more men friends than they do women friends.

The area that are red or orange show the opposite trend, where people make friends with mostly the same gender as themselves.

Across genders, so male friends with females and vice versa.