Do not put all your eggs in one basket.
Put all your eggs in one basket, and watch that basket carefully.
Both are repeated constantly, usually by people who have not noticed they cancel out. A new investor stares at the contradiction and does nothing, which is at least an understandable response.
They are not competing pieces of advice. They are advice for two different people, living two different lives, and the thing that separates those lives is not risk tolerance.
It is attention.
What concentration actually requires
Concentrated investing has two preconditions, and they rarely turn up together.
The first is a base of capital large enough that winning would genuinely change your life. The second is that you understand one specific thing more deeply than almost anyone else does.
There is a third fact usually left out of the conversation, and it is the one that decides the matter: concentration is enormously expensive in attention.
A tenfold return on ten thousand dollars is ninety thousand dollars of gain. That is real money. It is nowhere near enough to justify the years of attention the bet demands — attention you could have spent compounding your own earning power, which for most people under fifty is by far the larger asset.
The same multiple on a serious base is life-changing. Only then is the attention well spent.
The second precondition is what separates a concentrated bet from a concentrated gamble. You hold because you can see something others cannot, and because that sight lets you sit through a fifty percent drawdown without flinching.
Very few people meet both conditions at once. Most of those who believe they are concentrating are, in fact, gambling — which is a perfectly respectable activity, provided the gambler knows that is what he is doing.
What diversification actually buys
Spread money across a basket wide enough and you receive the basket's average return. That much is in every textbook.
What the textbooks rarely say is what else it does.
It diversifies your attention — or rather, it releases it.
The real value of diversification is not that it earns the most. It will not. Its value is that it frees the resource you will miss most in every other part of your life.
When you choose it, the decision you are actually making is not which asset you have the most conviction in. It is this: you are giving up the ambition to beat the market, in exchange for getting your attention back, which you can now spend on the parts of your life that will matter more in thirty years.
That is a trade, and it is a good one for most people. But it should be made consciously, as a trade, rather than absorbed as a default because somebody said not to put all your eggs in one basket.
The position that is neither
The genuinely dangerous place is the middle, and it is where most portfolios sit.
A person holding eight individual stocks has spread the money a little, but a small number of holdings may still leave substantial concentration risk. He carries most of the idiosyncratic risk of picking, along with little of the upside that would justify it — and he pays the full attention cost, because eight positions demand watching in a way an index fund does not.
He has bought the cost without the prize.
The honest test is uncomfortable and takes about a minute. Look at the portfolio and ask: if my single largest holding fell seventy percent tomorrow, what would change?
If the answer is not much, you are diversified, and you should stop reading about it.
If the answer is my retirement moves by five years, you are concentrated — which is a legitimate position, but only if you can also state, in a sentence, what you understand about that holding that the market does not.
If you cannot answer that second question, you are not concentrated. You are exposed, and the difference is that concentration is a decision while exposure is something that happened to you.
The part that is not about money
There is a version of the diversified investor who is worse off than the concentrated one, and it is worth naming.
It is the person who diversified, freed the attention, and then spent it on the market anyway — checking a broadly diversified portfolio daily, reading commentary about an index they have committed to holding for thirty years, extracting all of the anxiety of active investing and none of its returns.
That person has paid the cost of both strategies and collected the benefit of neither.
Diversification only works as a trade if you actually take delivery of the other half of it.
Buy the basket. Then go and do something else — which was the entire point of buying the basket.
Adapted from The Money Script by Paul Yang. See the books.