Every safe bet has an “until”

Here is the most honest investment advice I know. Every line of it is true.

• It's an excellent idea to invest in stocks… until the market crashes.
• It's an excellent idea to invest in gold… until you need to sell it.
• It's an excellent idea to invest in ETFs… until the fees eat your returns.
• It's an excellent idea to invest in bonds… until the issuer defaults.
• It's an excellent idea to invest in mutual funds… until the star manager quits.
• It's an excellent idea to invest in real estate… until the "unforeseen" happens.

One list is never enough, so here's a second:

• It's an excellent idea to invest in value stocks… until they become value traps.
• It's an excellent idea to invest in index funds… until you're stuck in a lost decade.
• It's an excellent idea to invest in small caps… until liquidity dries up.
• It's an excellent idea to invest in foreign markets… until currency swings wipe you out.
• It's an excellent idea to invest in commodities… until storage costs exceed the gains.
• It's an excellent idea to invest in TIPS… until actual inflation outruns the reported rate.

Every asset has an "until". Returns and risks come as a pair, and you don't get to chase one without carrying the other. The trouble starts when a product makes the "until" invisible. Index funds have done exactly that.

The comfortable lie

ETFs are a lie we tell ourselves about risk. Not a malicious lie; a comfortable one.

They're cheap and simple, and they really do stop you from blowing up on a single bad stock. I've used them and I still do. But the more I watch how markets actually work, the more I think we've collectively mistaken a different kind of risk for safety.

When money flows into an index fund, the algorithm doesn't think. It buys in proportion to size. The biggest company gets hundreds of times more capital than a mid-cap with better margins, faster growth and stronger fundamentals. Not because anyone evaluated them, but because one is already big and the other isn't.

Do that every day, across more than half the market, and you stop getting price discovery. You get a self-reinforcing size contest. The biggest get bigger, not because they're the best businesses, but because they're already the biggest.

The loop

Some researchers argue this creates mechanical price momentum that compounds into structural distortion: a pipeline that inflates large caps simply by existing, independent of the underlying business. The reflexivity is real. Higher prices mean cheaper capital, a stronger acquisition currency and a bigger talent magnet. The algorithm creates the fundamentals it was supposed to reflect.

Critics push back, reasonably. Active players still set prices at the margin: hedge funds, levered funds, arbitrageurs. When prices drift too far from fundamentals, short sellers correct them. And the "market instability" threshold some models cite lacks broad academic consensus. Fair points, all of them.

But here's what I keep coming back to: the stabilising power of active capital depends on its relative size. As the passive share grows, that power shrinks. The correction mechanism weakens, even if it never disappears entirely. Passive now controls around 54% of the market and grows by roughly 4% a year. Do the maths.

When the flows reverse

There's a second engine under all this. Flows have stayed one-directional for decades because working populations pay into pensions every month. Demographics will eventually reverse that. When they do, the same amplification that inflated large caps on the way in will work in reverse on the way out.

My honest view: ETFs are a tragedy of the commons dressed up as prudent investing. Individually rational, potentially collectively destabilising.

When you buy a broad index today, you aren't buying the best businesses. You're buying the most hoarded ones, assets whose valuations are partly self-reinforcing rather than grounded in cash flow. Strong companies outside the index are systematically starved of capital. Not because the market judged them, but because the algorithm never looked.

The product feels like risk mitigation. What it actually does is trade one kind of risk for another, quietly and invisibly, over decades. You only find out which kind was worse when the tide turns.

So what do you do?

I won't hand you a portfolio. But the lists at the top point to the only rule I trust: don't chase returns without understanding the risks, because they're inseparable. And invest in what you believe is undervalued. You may be wrong, but at least you'll be honest with yourself about why you own it.