Kelly's time at Westpac, and St. George before that, has been a successful stint by almost any standard.

Revenue and profits have grown nicely and many shareholders raise a virtual (or real) glass to Ms Kelly every six months when the dividends roll in.

Whether or not she'd want to actively claim it (and I suspect she might, unless modesty prevented it), Gail Kelly has been a trailblazer for women, too. She's shattered the glass ceiling when it comes to women in senior management positions at the pointy end of corporate Australia, and I know from personal experience she has been a role model for many women in business.

Her absence from the big end of town does leave a large gap when it comes to the representation of women in those corporate positions, and that's a shame.

Merit wins

You won't get any argument from me that merit should win when it comes to senior management positions. Those appointments should be made irrespective of race, gender, religion or anything else that doesn't relate to the person's ability to do the job.

Unfortunately, there's little doubt that conscious and subconscious decisions have meant that women remain sorely underrepresented in the management ranks and around the board tables of corporate Australia.

From a societal perspective, anything that prevents us from equality of opportunity is a problem that needs to be addressed. But even from a coldly financial perspective, homogeneity is a bad thing.

The old adage, "When we all think alike, no one thinks very much" certainly rings true.

Who's thinking?

If you have a group of decision makers who share a significant proportion of their life experience in common, you'll have fewer new ideas. When a company is dominated by a single way of thinking, you'll probably struggle to see new ways of doing things. And when trouble comes - as it inevitably will from time to time - you'll have many fewer potential solutions.

And honestly, if you directly or indirectly make it tough for a group of people to rise to the top, you simply reduce the available pool of talent - and on average, you'll likely lower the quality of your top brass.

Far from being just an interesting exercise, this very area has significant potential implications for investors.

When you're considering buying shares in a company, you should be checking out its directors and management. Ask yourself if you trust them. If they have a good track record. If they seem to have a plausible and attractive strategy. What their experience is like. Not just industry experience (although that's very important), but life experience.

Bang, bang

They say that to a man with a hammer, every problem looks like a nail. So you can reasonably expect that to a room full of homogenous people, the problem and its solution will be reasonably narrowly defined.

Charlie Munger, the Berkshire Hathaway vice chairman and Warren Buffett's right-hand man is a noted polymath. He has long championed the cause of bringing many different disciplines into play when trying to make the best possible decisions.

If the problem is indeed a nail, the hammer 'solution' is straight-forward.

But when the problem isn't a nail, you'd better hope your company's upper ranks are full of different types of people with different experiences and perspectives. Otherwise you'll end up with an unsolved problem - and holes everywhere.

The problem doesn't stop with companies, though. If you were an expert buggy-whip maker, you may well have missed the car revolution while you invested only in the best buggy-whip shares you could find. The best bookstores in the world are feeling pressure from the internet, no matter how good they are, and shareholders are getting crunched. And the 'new normal' of high-debt property trusts was violently realigned in the wake of the GFC.

Foolish takeaway

As an investor, you don't have to be able to see around corners. But the more you can include different perspectives and disciplines, the better prepared you'll be when it comes to thinking about just what might be coming around that corner, and how you'll respond to it.

As Louis Pasteur commented, "Fortune favours the prepared mind".

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Scott Phillips is a Motley Fool investment advisor. You can follow Scott on Twitter @TMFGilla. The Motley Fool's purpose is to educate, amuse and enrich investors. This article contains general investment advice only (under AFSL 400691).