Women and men are not actually split evenly around the U.S.
Depending on the location and the age group, some places have a lot more women than men, and vice versa -- as a fascinating series of maps by Dadaviz's Jishai Evers shows.
Evers used data from the U.S. Census to create the gif below, showing places in the U.S. where there are more women than men, and vice versa, for different age groups.
The counties with more men than women are shown in blue, and the counties with more women than men are shown in pink. The graphic cycles through maps for Americans of different age groups, starting with people who are five years and younger and ending with people who are 85 years and above.
The animation shows the map changing from predominantly blue (male) to predominantly female (pink) as it focuses on older age groups. The reasons behind this change are complex and fascinating.
First, let's look at why the map starts off blue. At birth, odds are slightly better than even that a baby will be a male. According to the Centers for Disease Control and Prevention, the overall chance of having a boy is 51.2 percent, meaning that for every 1,000 girl babies born, there will be 1,050 boys.
That ratio can be affected by a few different factors, including the age and race of the mother, as well as the birth order of the child. According to the CDC, the percentage of male babies tends to decrease with birth order -- meaning a woman's first child is slightly likelier than her sixth, seventh or eighth child to be a boy. The CDC also found that younger and older mothers (women younger than 15 and older than 35) are slightly more likely to have a girl than mothers between the ages of 15 and 35.
So-called "sex selection" -- choosing to have a boy or girl baby through in vitro fertilization or selective abortion -- may also influence the sex ratio. As poll by Gallup in 2011 shows, more Americans prefer having boys to girls, a preference that has actually changed little since the 1940s.
So slightly more babies are boys than girls, which explains why the map starts out so blue. But why does it quickly become so pink?
The reason is that women have a significantly longer life span than men. In 2014, the average life expectancy for men in the U.S. was 77.11 years, while the figure for women was 81.94 years, according to the CIA World Factbook.
At 85 and older, women actually outnumber men two to one. Men still tend to be wealthier and earn more money than women in the U.S., and researchers say the age gap between women and men would be even bigger if women and men were on equal economic footing.
There's a variety of reasons for these trends. Some are biological -- men appear more likely to die of heart attacks and strokes, for example. Other reasons are social. Men are more likely to take on dangerous jobs, like logging and mining. They tend to engage in riskier behavior than women, like driving fast and using illicit drugs. Men are also more likely to die through violence, like homicide or war.
This higher rate of death means that women outnumber men in the U.S., making up 50.8 percent of the U.S. population in 2013.
There are also certain states that attract more men than women, largely because of the local jobs or lifestyle. Men predominate in the West: Alaska, Wyoming, North Dakota and Nevada all have significantly more men than women.
Here's a more detailed look at Evers' maps:
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