In the comments to the post on nudity in movies, I noted that of all the things that girls are willing to change about their appearance when they play dress-up for '80s night, their hairstyle is off limits. Maybe they'll put it in a ponytail to one side, but that's it. In three years of almost weekly attendance, I've seen a girl with crimped hair less than 5 times. They just won't alter the length, how straight vs. wavy it is, or how close to the scalp vs. how mane-like it is. Of all ethnic markers, hairstyle must be one of the most inviolable.
Just to remind those who were there, or bring it to the attention of those who weren't, here's what we imagine when the hairstyles of the wild times come to mind. They're all examples of Big Hair, whether from the '60s or the very early '90s:
Then that died off and was replaced by more moderate length, super-straight, and hugging-the-scalp hairdos during the mid-late '90s (already evident by the time Clueless came out in 1995) and the 2000s (one of my tutorees around 2006 said that she and her friends, before going out for the night, were going to make their hair "super super straight... like, Mean Girls straight").
So my first thought was that there's something about Big vs. Small Hair that responds to how wild the culture is. But that would imply that the '90s and 2000s should have been known for very short hair, and they weren't. In fact, when you think of cropped hair, you also think of the '60s through the '80s:
You also saw this split between the rising-crime era of the Jazz Age, when bobbed hair exploded in popularity alongside more luxuriant styles, vs. the mid-'30s through late '50s period of plummeting crime.
So how do hairstyles respond to the level of wildness in society? There's no strong shift toward either Big or Small Hair on average. Rather, the variance increases when crime soars and people are more wild. The average girl may have a pretty similar hairstyle during dangerous times, but there are a lot fewer people at that average level and a lot more who've ventured out into the extremes of tent-like hair as well as boyishly cropped hair.
This is one example of greater cultural and social conformity when times are getting safer, the chief example there being most of the 1950s, and this decade will probably be just about as bad. When the world gets more dangerous, people discount the future more, and part of that means not caring as much about how their present actions will affect their reputation down the line, in general. Being less constrained by worries about what everyone else will think about them, people let loose, branch out, and do their own thing more in dangerous times.
In safer times, people do get more varied in some areas, but this is not due to a shrinking concern for what others think -- rather, it is due to the opposite, whereby sheltered and complacent people spend more effort trying to broadcast their epic authentic uniqueness in an attempt to climb one rung higher on the status ladder. If they truly did care less than before about what others thought of their behavior, then they'd be more promiscuous. But as I've pointed out forever, promiscuity surges during dangerous times, the logic of which I elaborated on in a post below.
It would be worth quantifying this effect. You could take the covers of Vogue, or Playboy playmates, or something, and measure the volume of hair on girls' heads. Lump girls of a single year of Vogue (or whatever) into one group, and then find the variance in their hair volume. Plot that over time, alongside the homicide rate, and see how close the impression comes to reality.