Does “just SIP the index” still work — and what happens when everyone does it?
There is one piece of advice you hear everywhere now: stop picking stocks, stop picking funds, just put money into an index every month and wait. The data behind it is strong. But advice has grown into something bigger than the data, and the gap between the two is where the risk hides.
Let me use one simple picture for the whole thing.
Think of the stock market as a giant vegetable market.
- An active fund manager is a careful shopper. She picks only the best tomatoes and hopes to beat everyone.
- An index fund is a lazy shopper. He buys one of every vegetable. No thinking, very cheap.
- SIP is a huge crowd. It shows up every single month and buys — rain or shine, cheap or costly.
Now the three real questions.
- Does careful picking still beat lazy buying?
For the big, famous vegetables — large companies — no. The careful pickers almost always lose.
In the US, about 79% of active large-cap funds lost to the S&P 500 in 2025, the fourth-worst year for stock pickers in 25 years. Stretch it out and it gets brutal: roughly 92% of US funds lost over 20 years [1].
Why? Everyone is already watching the big stalls. Hundreds of analysts cover every large company. There are no secret bargains left. So, you may as well buy the lazy basket and save the fees.
But here is the part the headline skips. For the small, unknown vegetables — small companies — careful picking can still win, because nobody is watching those stalls.
In India in 2025, active mid- and small-cap funds beat their index — their best year since 2014 [2]. The catch: stretch that to ten years and even they lose about four times out of five [2]. And a chunk of the 2025 win was luck, not skill — the small-cap index fell hard, and active funds simply fell less.
So, the real rule is not “index always wins.” It is this:
Lazy buying wins where everyone is looking. Careful picking has a chance where nobody is looking.
The index is strongest exactly where the market is most efficient. It is weak where the market is sleepy. That is not a flaw in the data. That is the whole mechanism.
- What does the giant monthly crowd do to prices?
The crowd is now enormous. In India, about ₹31,000 crore flows in through SIPs every month, it has kept buying for more than 60 straight months, and it now makes up about a fifth of the whole industry’s money [3]. Domestic investors have even overtaken foreign investors on how much of the market they own [3].
This crowd has two faces.
The good face: it is a cushion. The crowd buys no matter what. So, when foreigners panic and run, the crowd keeps buying and holds prices up. When the Indian market fell about 11% in early 2026, the crowd did not flinch — it kept buying right through the fall [3]. That is real stability, and it is new.
The bad face: the crowd never checks the price tag. It buys a vegetable whether it is cheap or three times too expensive. And here the research gets uncomfortable.
Two finance professors, Gabaix and Koijen, studied what flows do to prices. Their finding shocked the field: every ₹1 (or $1) pushed into the market can lift the market’s total value by around ₹5 — far more than old textbooks said, and the push does not fade [4].
A second study, published in the American Economic Review, measured why. As money has moved from careful buyers to lazy ones over 20 years, the market has become about 11% “stiffer” — meaning the same flow now moves prices more, not less [5]. Fewer hands are left to push back on a silly price.
(To be fair, not everyone agrees that the effect is this large. Some market-structure researchers argue the real multiplier is closer to 1, not 5 [6].)
The market commentator Michael Green adds the sharpest warning. The crowd’s money is “price-blind,” he argues. It does not buy each stock equally — it pushes the biggest, most-traded names up the most, which makes them even bigger, which pulls in even more money. A spiral. And spirals run both ways. The same machine that lifts prices on the way in slams them down on the way out.
So, does the crowd create new gaps? Yes — two.
The first is a truth gap. In India today, big companies look fairly priced, but many small ones are puffed up — held high only because the crowd keeps shoving money in, even as the actual businesses underneath weaken [7]. Prices have partly stopped telling the truth.
The second gap is good news for a careful buyer. Because so much money is now price-blind, the quiet, ignored corners of the market stay mispriced for longer. That is exactly where a patient, price-conscious investor can still find a real bargain.
The one danger to respect: this crowd has never lived through a long, painful, multi-year fall. Sixty good months is a habit, not a full cycle. The cushion holds today. Nobody has tested what happens if it ever turns into a seller.