Secretary of State Hillary Rodham Clinton serves as further proof that women do not have to kowtow to expectations, rules of thumb or other quietly bullying cultural assumptions. She is a role model for women who are past the ingenue phase of their lives. She is making a fashion statement.

Clinton, at age 62, has grown out her hair. And it looks quite nice.

Conventional wisdom advises that after a certain age – 50ish – women should cut their hair. It’s impossible to trace this bit of advice to the first tyrant who uttered it.

But over generations, it has become ingrained in beauty lore. Some women might continue to wear flowing hair deep into their AARP years, but they do so knowing they’re flouting accepted practice.

This belief remains stubbornly unchanged despite a generation of salon owners who’ve grown hoarse explaining that hairstyles should be tailored to the individual.

The axiom survives despite bountiful evidence of its wrongheadedness: Take note of elegantly aging women such as Catherine Deneuve, Patricia Clarkson, Meryl Streep. The cut-your-hair mantra has nothing to do with whether it is thin or lush, streaked with gray or luminous with $500 highlights.

It’s not a friendly nudge to make sure a woman doesn’t get mired in her own past. Just cut it.

The abundance of short coifs on women of a certain age is especially pronounced in Washington and in politics, where there are fewer creative iconoclasts, rule-breakers and eccentrics who simply don’t care what others think.

For years, Clinton had a softly layered style – one with volume on top that flowed gently inward to the nape of the neck. It was a look she settled on after years of dealing with the public’s obsession with her headbands, her bangs, her bob.

She finally found a style that was a keeper, and even loosed her own wry humor over the outsize media interest in a woman’s right to play with her hair. What does it all mean? Nothing. Everything.

Some variation of Clinton’s layered cut is still favored by women such as presidential adviser Valerie Jarrett to Michigan Gov. Jennifer Granholm.

It is as though it is the officially vetted hairstyle for public life, certain not to generate comment in the manner of Sarah Palin’s hair – golden highlights glinting from a tousled up-do – or former Secretary of State Condoleezza Rice’s shoulder-grazing, steely flip.

Clinton’s hair, now creeping toward below-the-shoulders territory, is practically radical for Washington’s seasoned female power elite.

Good for her.

In our cultural vocabulary, long hair signifies youth, femininity and sex appeal. No wonder it’s far and away the favorite of Hollywood stars.

By contrast, shorter hair is serious, sophisticated, strong.

Cultural pressure to submit to the scissors after a certain age seems rife with an unkind and unspoken subtext that because long locks are a sign of vibrancy and sexiness, it’s a social contradiction to see such styles on women who have wrinkles and crow’s-feet.

Another popular argument is that long hair drags down the face – and a face that is showing the effects of gravity should steer clear of anything that might make it look even longer in the tooth.

Throw into the conversation the attitude that long locks are tools of flirtation. They are a handy excuse for a toss of the head; a strand might have to be girlishly flicked out of one’s eyes or coyly tucked behind the ear.

May a 60-year-old woman flirt? Or does her age imply that she must be beyond that sort of giddiness?

Fashion stylists often admonish their clients to dress appropriately for their age. But in an era when many 40-year-olds have more toned and fit physiques than a lot of teen-agers, the question becomes: What determines whether something is age-appropriate?

Women have been known to weep over a bad haircut. They will nod in sympathy when a friend confides that she’s having a bad hair day. The decision to cover gray strands – or not – can tap into self-confidence and the way in which they will engage with the world.

Maybe that’s why folks were so obsessed with Clinton’s hair during her days as first lady. Why did she seem so unsettled about something that’s so personal?

There’s no desire here to try to delve into the secretary’s psyche by focusing on her longer hair. So defenders of a woman’s right to be fickle about her hair can stand down.

Whether Clinton’s new style is feminine or pretty or soft are matters of personal opinion. What resonates more broadly is the length.

Somewhere between chin-length and shoulder-grazing, a hairstyle became a silent reminder that cultural assumptions do more damage to women as they age than any poorly chosen frock ever could.